Just this month when a Netmums user posted a clip of her baby gasping for breath - the comments were for the most part all about the importance of vaccination.
I'd like to clarify now, the focus of this post is not infant vaccinations; the subject that always causes a trench like divide. I have to briefly touch on them, in order for the piece to make sense - but the key messages I want to convey are:
- The truth I'm going to share with you is equally as valid, regardless of which side the debate you sit.
- Many of those who suffer most seriously with whooping cough are too young to be fully vaccinated, just like the baby in the Netmums clip, so it's a moot point. I know at this point some will yell "pregnancy vaccinations" - but I will come on to those later, and why again regardless of your view the information I'm sharing is still just as important.
The commentary with the video footage suggested that baby had received his first shot as scheduled, which is estimated to be around 55-70% effective - but three doses are needed to reach an average quoted protection rate of around 80%. Immunity to whooping cough wanes fairly rapidly and so boosters are given to "top up" antibody levels..
The UK:
Delivers doses at 2, 3 & 4 months, with a pre-school booster between 3-5 years. NHS
The USA:
Delivers doses at 2, 4, 6 months, with an additional vaccine between 15-18 months, and a pre-school booster between 4-6 years. A second booster is given 11-12 years. CDC
This means the earliest age a baby can obtain any protection via their own vaccination is 2 months.
One of the problems we face with whooping cough, and something we need to understand when discussing tactics to protect the young - is that unlike with other diseases, herd immunity from vaccinations alone may not be a viable strategy. Whereas sometimes the plan to vaccinate everyone around the most vulnerable group can prevent spread to newborns, this is very difficult to achieve with pertussis for a few reasons.
Initially vaccination against pertussis was done with what is called a whole cell vaccince, but due to reported side effects, an acellular vaccine was introduced. If you want all the science behind that, you're welcome to Google - but the upshot is the new version isn't quite as effective as the old.
A 2013 FDA study suggests that the acellular vaccine isn't able to prevent the bacteria from getting into your system if you're exposed to the disease, but it is capable of preventing or significantly reducing symptoms, i.e. it stops the vaccine recipient suffering pertussis or results in a milder case.
As for breastfeeding rates during this period; Dr Valerie Fildes who has undertaken pioneering work in this area and written widely on the subject, notes that by by 1940 around 60% of mothers initiated breastfeeding, but many quickly weaned their babies on to solid foods.
Therefore you would think, or at least I would, that if there was something else we could do as well to protect babies, we would all know about that too?
Doctors and midwives would surely share all the information we have on keeping the most vulnerable safe, right?
Like Harry Potter's Voldermort, nobody seems to want to mention breastmilk as a public health measure against whooping cough. Of course providing breast milk isn't as straightforward as giving a shot, but how many parents or even doctors are fully aware of the impact infant feeding has on pertussis rates and outcome?
Some even dismiss breastmilk as being ineffective in protecting babies against pertussis, so let's take a look.
A 1985 review concluded that maternal antibody transfer through colostrum may indeed be a method of protecting human infants from pertussis during the first few months of life. They explored amongst other things a paper by Dowham et al, who hypothesised that as infants inhale milk feeds and regurgitate them through the nose, the antibodies collecting in the respiratory tract (remember those sticky IgA antibodies we talked about?) might protect against severe respiratory infection.
A 2010 study found colostrum samples showed 100% average transfer rate of IgG antibodies, and variable levels of IgA antibodies, depending on the degree of exposure that each mother has had to several antigens. Overall high antibodies levels demonstrated a high rate of protection, whilst lower levels weren't as reliable.
Well, researchers have found that vaccinating mum during pregnancy, does as proposed increase the levels of both IgG and IgA pertussis antibodies in her breastmilk; what's more, unlike the more rapidly waning antibodies passed via the placenta, they're not short lived:
One study states:
The 2010 study I mentioned reached similar conclusions when they tested a colostrum sample from a woman with immunodeficiency. Although she didn't produce IgA antibodies at all, her colostrum still protected 45% of mice against pertussis. Similarly purified IgG antibodies protected only 65% of the mice, leaving researchers to conclude:
Researchers who published in the the Journal of Vaccines & Vaccination in 2015 certainly seem to think so.
Their paper reads:
Ultimately anyone who believes it's important to try and protect tiny babies from pertussis, surely has to acknowledge that feeding method has a role to play. However uncomfortable that might make us feel.
Why are midwives not telling parents at their antenatal sessions? I would surmise that most (and certainly those I checked in with) don't know - nobody bothered to pass on these facts. Are we so worried about "guilting women" as some doctors claim, that we feel they can't handle the research?
Even in educational videos about preventing pertussis produced by children's hospitals such as this which has had over 126,000 views, breastfeeding is never even mentioned.
All this may become even more pertinent in light of several reports that the bacterium that causes whooping cough has evolved, which as a result may reduce the effectiveness of the vaccine.
If we explore what the UK have to say on the matter, we can look at the green book, chapter 24 which reads:
In Denmark, pertussis is only a notifiable disease under the age of two. A 2010 study found that B. pertussis infection may be under-diagnosed among older children and adults with coughs in Denmark - researchers tested samples from 178 patients and 3-12% tested positive. They had up to 12 times the levels of pertussis circulating than the UK in 1999, with no record of what circulating levels are now in those over 2, providing potentially more likelihood of natural boosting. If we then also consider that nearly 100% of mothers in Denmark initiate breastfeeding - I don't think we can really draw any direct comparisons to the UK - the reality is, as I see it that as of yet, nobody really knows for sure.
The other thing worth considering when discussing the big picture of pertussis, is parapertussis. This is another bacteria of the genus Bordetella, and produces similar symptoms to whooping cough but is generally milder.
However what has also come to light, is that unlike the old style pertussis vaccine, the new version doesn't induce the kind of immunity that prevents transmission. This means someone who is vaccinated yet not displaying symptoms, or worse has a mild case (complete with coughing, runny nose etc) is not diagnosed and yet can shed the disease to a vulnerable person - the vaccine only potentially protects the recipient, not other infants as it was previously thought.
As we can see on this slide - in the UK whilst cases in those older than a year old are reported to be incredibly low at points, there is still a significant number in those less than 3 months. Whilst the level falls somewhat, that age range is much more susceptible to the spikes of epidemics.
This means either:
Low levels circulating in society doesn't result in increased protection for newborns, or the reporting is inaccurate and more cases have actually taken place. If vaccinated people can indeed suffer as described without symptoms or presenting as a mild case, they are less likely to seek medical assistance. If they do, the the physician is less likely to query pertussis from a mild cough and a sniffle, even more so in older children and adults - thus these cases would not be recorded, but could be contributing to transmission spread.
Regardless of the ins and outs of why, during the 10 year period 2001-2011, 85% of deaths due to pertussis in infants occurred in infants who were too young to be protected by vaccination.
This means either:
Low levels circulating in society doesn't result in increased protection for newborns, or the reporting is inaccurate and more cases have actually taken place. If vaccinated people can indeed suffer as described without symptoms or presenting as a mild case, they are less likely to seek medical assistance. If they do, the the physician is less likely to query pertussis from a mild cough and a sniffle, even more so in older children and adults - thus these cases would not be recorded, but could be contributing to transmission spread.
Regardless of the ins and outs of why, during the 10 year period 2001-2011, 85% of deaths due to pertussis in infants occurred in infants who were too young to be protected by vaccination.
The CDC put this figure even higher at around 92% and the Center for Infectious Disease Research and Policy (CIDRAP) agree saying:
So we know that when it comes to infant pertussis, we have to think beyond infant vaccination - in fact we have to realise that all the noise about them, for babies who can't have them yet anyway - may be distracting us from exploring what could actually help.
We know babies get their very early immunity from mum via the placenta, and so exploring maternal levels gives us more insight; but that's not as simple as it sounds.
If you catch pertussis, current research suggests you are immune for 7-20 years, although a 2009 study disputed this conventionally held belief, instead they felt 30-100 years was possible; however as immunity is individual, many will lose immunity quickly and some never at all. Several papers find that in areas in which infection widely circulates (such as India), pregnant mums carry high numbers of pertussis antibodies, with the accepted rationale being this "wild exposure" keeps their antibody levels topped up, acting as a natural booster shot.
If you're vaccinated, research suggests immunity wanes a little more rapidly, with averages quoted of 4-12 years; the 2009 study concluded that unfortunately, their analyses were less conclusive about the average duration of vaccine-derived immunity. However, the data suggested it to be "generally shorter than the duration of natural immunity (and very short for the longest durations of natural immunity)" - again there is the potential for exposure to boost antibody levels - although of course as the incidence of disease falls, so does the chances of natural exposure. This means in order to achieve herd immunity via vaccinations alone, ie with disease eradicated and without wild strains circulating, one would need to re-vaccinate every member of the population every 4 years.
Many of mothering age today were vaccinated against pertussis, but haven't had a booster since childhood - some may have been exposed to the wild circulating strains and have high levels of antibodies, but others may not. Indeed studies have found very variable rates of antibody levels in mums tested.
A further problem we have with whooping cough, is that the exact levels of antibodies required for protection are not known. We know that when higher levels of antibodies against pertussis are present, we are less likely to suffer disease; however unlike for some diseases, there isn't a known target level, or a magic number we need to achieve, over which we know for sure people are protected.
So, in an attempt to overcome this variability, and try and ensure newborns received enough antibodies, and in response to significantly increased rates of disease in 2012, immunising mothers in every pregnancy was introduced in some countries, including America and the UK. Stimulating an immune reaction in mum, means increased antibodies are passed to baby that are thought to last for the first 8 weeks.
Immune systems aren't computers and as other studies note, some people lose immunity much more rapidly than others, or don't mount the expected antibody response.. Plus pertussis is cyclic and as we saw in earlier charts, levels typically fall after a particularly severe year.
Since implementation, a review examining outcome found this to be up to 90% effective in protecting newborns - although it should be noted the review included only 58 cases and 55 control infants. Some however predict this strategy may only be fully effective for the first month of life, for the following reasons:
Others note the high antibody levels stimulated via vaccination, immediately prior to birth should result in large amounts of antibodies that take longer to wane.
"With pertussis rates increasing over the past 25 years, the mortality burden has shifted to babies younger than 6 months who are too young to be vaccinated".This is also acknowledged by the UK government who say:
"Despite sustained levels of vaccine coverage above 95%, from 2010 an increase in pertussis activity was observed in England and Wales from October 2011 and continued into 2012".Professor John Watson, UK Deputy Chief Medical Officer said:
"Babies too young to start their vaccinations are at greatest risk from whooping cough. It’s an extremely distressing illness that can lead to young babies being admitted to hospital and can potentially be fatal"In 2013 the FDA confirmed that whooping cough rates in the United States had been steadily increasing since the eighties, reaching a 50 year high in 2012 - despite high rates of vaccination.
So we know that when it comes to infant pertussis, we have to think beyond infant vaccination - in fact we have to realise that all the noise about them, for babies who can't have them yet anyway - may be distracting us from exploring what could actually help.
We know babies get their very early immunity from mum via the placenta, and so exploring maternal levels gives us more insight; but that's not as simple as it sounds.
If you catch pertussis, current research suggests you are immune for 7-20 years, although a 2009 study disputed this conventionally held belief, instead they felt 30-100 years was possible; however as immunity is individual, many will lose immunity quickly and some never at all. Several papers find that in areas in which infection widely circulates (such as India), pregnant mums carry high numbers of pertussis antibodies, with the accepted rationale being this "wild exposure" keeps their antibody levels topped up, acting as a natural booster shot.
If you're vaccinated, research suggests immunity wanes a little more rapidly, with averages quoted of 4-12 years; the 2009 study concluded that unfortunately, their analyses were less conclusive about the average duration of vaccine-derived immunity. However, the data suggested it to be "generally shorter than the duration of natural immunity (and very short for the longest durations of natural immunity)" - again there is the potential for exposure to boost antibody levels - although of course as the incidence of disease falls, so does the chances of natural exposure. This means in order to achieve herd immunity via vaccinations alone, ie with disease eradicated and without wild strains circulating, one would need to re-vaccinate every member of the population every 4 years.
Many of mothering age today were vaccinated against pertussis, but haven't had a booster since childhood - some may have been exposed to the wild circulating strains and have high levels of antibodies, but others may not. Indeed studies have found very variable rates of antibody levels in mums tested.
A further problem we have with whooping cough, is that the exact levels of antibodies required for protection are not known. We know that when higher levels of antibodies against pertussis are present, we are less likely to suffer disease; however unlike for some diseases, there isn't a known target level, or a magic number we need to achieve, over which we know for sure people are protected.
So, in an attempt to overcome this variability, and try and ensure newborns received enough antibodies, and in response to significantly increased rates of disease in 2012, immunising mothers in every pregnancy was introduced in some countries, including America and the UK. Stimulating an immune reaction in mum, means increased antibodies are passed to baby that are thought to last for the first 8 weeks.
Immune systems aren't computers and as other studies note, some people lose immunity much more rapidly than others, or don't mount the expected antibody response.. Plus pertussis is cyclic and as we saw in earlier charts, levels typically fall after a particularly severe year.
Since implementation, a review examining outcome found this to be up to 90% effective in protecting newborns - although it should be noted the review included only 58 cases and 55 control infants. Some however predict this strategy may only be fully effective for the first month of life, for the following reasons:
- The placental transfer of IgG is specific and has variable efficacy; this means that cord blood levels can be as low as 20% of maternal levels or can exceed maternal levels by 200%
- Most data on placental transfer of antipertussis IgG date from the 1940s. These data demonstrated transplacental transfer of pertussis IgG at a relatively low efficiency. In only 2–12% of mother-infant pairs did the infants’ titres exceed maternal levels.
- More recent studies have shown conflicting results on the relative efficiency of the transplacental transfer of specific maternal pertussis IgG
- Pertussis notification data from the prevaccine era provide indirect evidence that maternal antibodies provide short lived protection against fatal pertussis by demonstrating that the rate of pertussis deaths in the first month of life was approximately one-third of that in the second and third months of life
Others note the high antibody levels stimulated via vaccination, immediately prior to birth should result in large amounts of antibodies that take longer to wane.
As for breastfeeding rates during this period; Dr Valerie Fildes who has undertaken pioneering work in this area and written widely on the subject, notes that by by 1940 around 60% of mothers initiated breastfeeding, but many quickly weaned their babies on to solid foods.
She says:
"The protection afforded by the Immunoglobulin A in mother’s milk was therefore short and the risk of ill-health heightened."All this means that even if we run with the absolutely best estimate of 90%, we have 10% still vulnerable. Plus we have the roughly 20% who are still not covered despite receiving their full set of vaccinations. And all that's assuming 100% uptake of the antenatal and postnatal vaccinations.
Therefore you would think, or at least I would, that if there was something else we could do as well to protect babies, we would all know about that too?
Doctors and midwives would surely share all the information we have on keeping the most vulnerable safe, right?
Like Harry Potter's Voldermort, nobody seems to want to mention breastmilk as a public health measure against whooping cough. Of course providing breast milk isn't as straightforward as giving a shot, but how many parents or even doctors are fully aware of the impact infant feeding has on pertussis rates and outcome?
Some even dismiss breastmilk as being ineffective in protecting babies against pertussis, so let's take a look.
Before we go any further we need to have a quick recap of antibodies. It's a bit dull so I will keep it brief, but it's pretty important to understand why breastmilk is so important:
- IgG antibodies are found in all bodily fluids including blood. They are the antibodies passed to baby across the placenta and are important in protecting against bacterial and viral infections.
- IgA antibodies are found on mucosal surfaces in areas of the body such the nose, breathing passages, digestive tract, ears and eyes. IgA antibodies are "sticky" in order to adhere to and protect surfaces that are exposed to outside foreign substances, and also provide important protection against infection.
- Babies are typically born with higher levels of IgG antibodies (passed from mum) but lower levels of IgA. In contrast breastmilk often has higher levels of IgA, and lower levels of IgG.
In 1989 a study found breastmilk contained "significant titres of specific IgG and IgA antibodies to pertussis"(along with flu, strep and meningitis)
A study that tested women 10 years post vaccination in areas with circulating strains, found 87% produced pertussis antibodies in their colostrum.
If mums are producing antibodies, they're also in their colostrum and milk; so the next question has to be, do they serve a purpose? i.e. can they help protect a baby against pertussis.
There are ample studies exploring the disease- preventing role of the antibodies in breastmilk, and some that have specifically explored the role of whooping cough antibodies.
There are ample studies exploring the disease- preventing role of the antibodies in breastmilk, and some that have specifically explored the role of whooping cough antibodies.
A 1985 review concluded that maternal antibody transfer through colostrum may indeed be a method of protecting human infants from pertussis during the first few months of life. They explored amongst other things a paper by Dowham et al, who hypothesised that as infants inhale milk feeds and regurgitate them through the nose, the antibodies collecting in the respiratory tract (remember those sticky IgA antibodies we talked about?) might protect against severe respiratory infection.
A 2010 study found colostrum samples showed 100% average transfer rate of IgG antibodies, and variable levels of IgA antibodies, depending on the degree of exposure that each mother has had to several antigens. Overall high antibodies levels demonstrated a high rate of protection, whilst lower levels weren't as reliable.
Researchers concluded:
"Our data demonstrated the effectiveness of anti-pertussis antibodies in bacterial pathogenesis neutralization, emphasizing the importance of placental transfer and breast-feeding in protecting infants against respiratory infections caused by Bordetella pertussis."So what about mums vaccinated during pregnancy?
Well, researchers have found that vaccinating mum during pregnancy, does as proposed increase the levels of both IgG and IgA pertussis antibodies in her breastmilk; what's more, unlike the more rapidly waning antibodies passed via the placenta, they're not short lived:
One study states:
"Interestingly, antenatal maternal vaccination appears to positively influence the production of specific antibodies transferred to the infant via breast milk for at least 5–6 months postpartum [71–73]"
But it gets even more interesting when talking about breastmilk and pertussis than just antibodies.
One study found that "human milk, unlike cow's, could reduce the viability of pertussis" - however they noted that "This antibacterial activity was not due to the presence of antibiotics or antibodies in the human milk".
One study found that "human milk, unlike cow's, could reduce the viability of pertussis" - however they noted that "This antibacterial activity was not due to the presence of antibiotics or antibodies in the human milk".
The 2010 study I mentioned reached similar conclusions when they tested a colostrum sample from a woman with immunodeficiency. Although she didn't produce IgA antibodies at all, her colostrum still protected 45% of mice against pertussis. Similarly purified IgG antibodies protected only 65% of the mice, leaving researchers to conclude:
"bacterial neutralization may not be solely because of the functional activity of specific antibodies, and suggests that other anti-infective factors present in human serum and colostrum may contribute to non-specific bacterial neutralization. Several non-specific anti-infective components capable of inhibiting bacterial pathogenesis have been found in human milk".Doesn't that mean if we add breastmilk with antibodies, to the "unknown factors in breastmilk that appear to neutralise bacteria", we have pretty hefty protection?
Researchers who published in the the Journal of Vaccines & Vaccination in 2015 certainly seem to think so.
Their paper reads:
"The dawn of maternal vaccination is an important milestone in breastmilk immunity. Breastmilk per se has immunopotential that protects the infant from important childhood diseases both in the immediate neonatal period and in the long term. Its immune nutritive attributes confer this exclusive early nourishment a cutting edge in defence that no other human nutrient can yet offer."
They go on to review evidence that breastmilk is important for the maturing immune system and its potential to differentiate harmless and pathogenic microbes, as well as its antimicrobial action.
They state:
"The immunological components in breastmilk are many. There are diverse and multifunctional. It is proposed that vaccines that are given to the mother can pass through breastmilk and potentially utilise these breastmilk components to augment action and protection."
and
"The increasing global incidence of antibiotic resistance to treat important infections affecting the infant makes it crucial to emphasize the importance of breastfeeding and possibly enhancing microbial protection transferred through maternal vaccination as a primary preventive strategy"They conclude that more antenatal clinics should routinely practise the delivery of this multi-pronged system as "primary disease prevention is achieved both by breastfeeding and by vaccination. "
Ultimately anyone who believes it's important to try and protect tiny babies from pertussis, surely has to acknowledge that feeding method has a role to play. However uncomfortable that might make us feel.
Why are midwives not telling parents at their antenatal sessions? I would surmise that most (and certainly those I checked in with) don't know - nobody bothered to pass on these facts. Are we so worried about "guilting women" as some doctors claim, that we feel they can't handle the research?
Even in educational videos about preventing pertussis produced by children's hospitals such as this which has had over 126,000 views, breastfeeding is never even mentioned.
All this may become even more pertinent in light of several reports that the bacterium that causes whooping cough has evolved, which as a result may reduce the effectiveness of the vaccine.
Evolved how?
Pertactin or PRN is a protein produced by pertussis bacteria, that helps them attach to the lining of the airways. PRN is an important component of the pertussis vaccine. (CDC).
A 2014 study analysed 320 bacteria samples from patients with whooping cough. The proportion of pertactin-free bacteria rose from five per cent of cases tested in 2008 to 78 per cent in 2012. Pertactin-free strains of pertussis have also been detected overseas, including in countries such as France and the United States.
Associate Professor Lam, co-author of the study. said that currently:
"There is no evidence that the pertactin-free strains are more harmful than other strains, and it is not yet clear whether they reduce the effectiveness of the vaccine in the short or long term. More studies are needed to better understand the effects of vaccination on the evolution of the organism”In 2015, another study found that there was a significant association between vaccination and testing positive for a PRN negative strain. However as the CDC point out, as other components of the vaccine provide protection, it doesn't automatically mean the vaccine will fail.
If we explore what the UK have to say on the matter, we can look at the green book, chapter 24 which reads:
"Studies in the Netherlands and Australia have suggested that genetic changes have led to vaccine failures, but many people question these findings. If genetic changes had increased the rates of vaccine failure, one would expect to see those effects first in Denmark, which has for the past 15 years used a vaccine with a single pertussis antigen. To date, however, there is no evidence of increased vaccine failure in Denmark."This seems really rather simplistic though.
In Denmark, pertussis is only a notifiable disease under the age of two. A 2010 study found that B. pertussis infection may be under-diagnosed among older children and adults with coughs in Denmark - researchers tested samples from 178 patients and 3-12% tested positive. They had up to 12 times the levels of pertussis circulating than the UK in 1999, with no record of what circulating levels are now in those over 2, providing potentially more likelihood of natural boosting. If we then also consider that nearly 100% of mothers in Denmark initiate breastfeeding - I don't think we can really draw any direct comparisons to the UK - the reality is, as I see it that as of yet, nobody really knows for sure.
The other thing worth considering when discussing the big picture of pertussis, is parapertussis. This is another bacteria of the genus Bordetella, and produces similar symptoms to whooping cough but is generally milder.
We have always known that the pertussis vaccination didn't protect against parapertussis, but what has recently come to light is that the pertussis vaccination appears to hinder the body's response in dealing with the parapertussis bacteria, as well as potentially enhancing the performance of this pathogen. Researchers of the 2015 study concluded:
"Thus, we conclude that aP vaccination interferes with the optimal clearance of B. parapertussis and enhances the performance of this pathogen. Our data raise the possibility that widespread aP vaccination can create hosts more susceptible to B. parapertussis infection."
Although currently milder, increased cases of parapertussis are still going to increase the burden in terms of healthcare costs to a community, as parents seek diagnosis and healthcare providers run tests to identify the bacteria in question. Increasing breastfeeding and breastmilk feeding rates, is also likely to reduce incidence; in addition to the evidence already discussed, this paper found that mucosal immunity*, including IgA antibodies (as found in breastmilk) might play an important role in protecting against parapertussis.
What we do know is that pertussis in unpredictable, is cyclic in nature and epidemics can occur. We also have to acknowledge that achieving very high rates of maternal vaccination may be difficult to achieve, and that any longer-term implications of this are still yet to be fully understood. As breastfeeding appears to offer some level of protection with low levels or even without antibodies present, all parents should receive this information - whether they plan to vaccinate themselves and their baby or not.
Therefore the question we have to ask is can we truly make informed choices about how we feed our infants, without transparency about a disease like pertussis?
- Duration of immunity against pertussis after natural infection or vaccination.
- The number of deaths among infants under one year of age in England with Pertussis, Results of a Capyure/Recapture analysis for the period 2011-2011
- Estimating the Duration of Pertussis Immunity Using Epidemiological Signatures
- Duration of Protection After First Dose of Acellular Pertussis Vaccine in Infant
- Passive Acquisition of Protective Antibodies Reactive with Bordetella pertussis in Newborns via Placental Transfer and Breast-feeding
- Pertussis surveillance report 2010
- Breastfeeding Reduces Risk of Respiratory Illness in Infants
- Different Effects of Whole-Cell and Acellular Vaccines on Bordetella Transmission
- Class-specific antibodies to Bordetella pertussis, Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis in human breast-milk and maternal-infant sera.
- Antimicrobial effect of human milk on Bordetella pertussis.
- Breastfeeding as a Tool that Empowers Infant Immunity through Maternal Vaccination
- The case for maternal vaccination against pertussis
- A case-control study to estimate the effectiveness of maternal pertussis vaccination in protecting newborn infants in England and Wales, 2012-2013.
- Role of Maternal Pertussis Antibodies in Infants
- Mother’s milk and infant death in Britain, circa 1900-1940
- Rapid Increase in Pertactin-deficient Bordetella pertussis Isolates, Australia
- Epidemic Pertussis in 2012 — The Resurgence of a Vaccine-Preventable Disease
- UK Green Book, Chapter 24, Pertussis
- OECD Family database - Social Policy Division - Directorate of Employment, Labour and Social Affairs CO1.5: Breastfeeding rates
- Seroprevalence of Pertussis among Danish Patients with Cough of Unknown Etiology
- Acellular pertussis vaccination facilitates Bordetella parapertussis infection in a rodent model of bordetellosis
- Role of Systemic and Mucosal Immune Responses in Reciprocal Protection against Bordetella pertussisand Bordetella parapertussis in a Murine Model of Respiratory Infection
- Housey M, Zhang F, Miller C, Lyon-Callo S, McFadden J, Garcia E, Potter R (2014) Vaccination with Tetanus, Diphtheria, and Acellular Pertussis Vaccine of Pregnant Women Enrolled in Medicaid — Michigan, 2011–2013. Morbidity and Mortality Weekly Report (MMWR). 63(38); 839-842.
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