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Breastfeeding and Vaccine Efficacy: why you need to read like a scientist.

January 29, 2012
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Two studies came out in 2010 (just now recently highlighted in the media) regarding the efficacy of the oral rotavirus vaccine among nursing mothers in developing countries. The studies found that among infants in India and Indonesia nursing actually inhibits the effects of the vaccine, leading to a blanket conclusion, quoted from one study, that “Strategies to overcome this negative effect, such as delaying breast-feeding at the time of immunization, should be evaluated.” Of course, this lead to immediate outrage and cries from breastfeeding advocates (and vaccine opponents) that 1) how could scientists even begin to suggest that vaccines are more important than breastfeeding? Look at all the research! and 2) see? you shouldn’t vaccinate anyway. See an example of a gut reaction from Natural News here. And of course, my initial reaction was the same, what about all the benefits of breastfeeding? Can’t breastfeeding help to naturally immunize and has maybe more overall health benefits than one vaccine?

But let’s examine the articles, objectively. The studies are examining a population of mothers and infants in countries where this disease, Rotavirus, is the cause of more than 85% of deaths in developing. Not so much in the US, or other devloped nations. The Rotavirus vaccines, Rotarix and Rotateq, have been shown to be highly effective in preventing severe diarrhea and hospitalization in young children in these low to middle income countries (as well as our own). There is however, a reduced efficacy in Asian countries, which these studies have linked  to high titers of a neutralizing antibody in breastfmilk at day 1-7 post partum (where the effect then begins to drop off). Neutralizing antibodies are a result of the high prevalance of the disease in these countries and the exposure of the mom so that she has high levels of antibodies to the virus. These antibodies are transferred through her breastmilk and neutralize or inhibit the vaccine response in her baby. US mothers tested did not demonstrate the same level of neutralizing antibodies, likely due to the lack of exposure to the disease. The authors make the conclusion that, based on these results, the high incidence and seriousness of the disease in these countries (India and Indonesia particularly), and the benefits of the vaccines, that mothers should delay or forego breastfeeding just before and until after the vaccine has been given and that a number of other factors could play a role in this finding.

Only they don’t say it like that unless you read the entire article. Usually, the general public only sees the abbreviated version of the article; a synopsis of the article that includes a brief introduction, decsription of the methods, results, and a general conclusion. And unfortunately, the conclusion basically states that vaccines and breastfeeding do not go hand in hand. In fact, the authors state, ” Results from clinical trials conducted in developed and middle income countries indicated that breast-feeding did not reduce the efficacy of either RV1 or RV5. However, the investigators only recorded whether or not an infant was breast-fed but not the interval between breast-feeding and the time the vaccine was administered. Our findings that mothers in America and Korea had no or only modest titers of neutralizing activity in breast milk also indicate that breast-feeding may not have a substantial negative impact in these high income settings.” “Some caveats should be considered in interpreting our data. First, we only examined antibody and neutralizing activity in breast milk from mothers in 4 countries; more specimens from other parts of the world including Africa and Asia should be examined to fully assess the potential negative impact of breast milk on live oral rotavirus vaccines in different settings. Second, while the observed high titers of antibody and in vitro neutralization activity of breast milk suggest a potential for substantial impact on vaccine performance, it is not possible to directly translate these findings into the real-world impact as this will be affected by many other factors such as the timing and amount of breast milk in the gut at the time of vaccination. Titers of neutralizing activity and antibodies decrease over time, so the effect we measure could also change over time or be neglected by administering multiple doses of the vaccine, perhaps at a time when the infant is not breast-feeding. Finally, we did not assess other factors such as interference of multiple bacterial and viral agents and different enteropathology in the gut of children in poor developing countries that might also potentially inhibit vaccine performance.” (Moon, et al.)

So in fact, if one reads the entire article, the authors admit that the findings are not completely linking breastfeeding and vaccine inefficacy. The authors of the second article suggest delaying of giving the vaccine until the titers lower (after day 7), or giving the vaccine directly after birth before the baby is fed colustrum. Another major point to remember when reading the findings is that these relate only to mothers in devloping countries, NOT the US. You can read the ABM president’s clarification/response to the article (and subsequent media response) here, which mentions the difference between the US population and developing countries, as well as interpreting the conclusions logically and rationally.

Evidenced-based care is so important, particularly where birth and breastfeeding are involved. There are social norms, cultural mores, and the overall opinion of “this is how we’ve always done it” that get in the way of real data that can benefit a new mother and baby. These articles show that evidenced-based care is also important to research all possible causes and links to the hows and whys of medicine today. Jumping to conlusions and generalizing are not helpful to anyone.

 

The links to the articles are here: (but if you want the PDF of the entire article, email me and I will send them on)

http://www.ncbi.nlm.nih.gov/pubmed/21147127

http://www.ncbi.nlm.nih.gov/pubmed/20442687

And a great collection of articles on how to read scientific articles from Science and Sensibilty:

http://www.scienceandsensibility.org/?tag=becoming-a-critical-reader

 

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One Comment leave one →
  1. StPaulieGrrl permalink
    February 8, 2012 10:41 pm

    I’d appreciate it if you could send me the full article: http://www.ncbi.nlm.nih.gov/pubmed/20442687
    I can’t seem to get anything but an abstract without paying a lot of money for it! Thanks!
    (ladybirchwood@gmail.com)

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