Canadian website wrongly links whooping cough vaccine to zika

Is a vaccine against whooping cough the "most likely triggering cause" of microcephaly in Brazilian babies? US fact-checking site Politifact couldn't find a shred of evidence to support this claim.

There are many unanswered questions about the connection between the mosquito-borne zika virus and microcephaly, a disorder in which a foetus’s brain does not develop properly in the womb. Not every baby of an infected woman develops this syndrome, and the mechanism by which the virus might affect the fetus is uncertain.

But moving around on the Internet is an entirely different take on the tie between zika and microcephaly. It doesn’t exist, according to certain blogs, tweets and articles on conspiracy-leaning websites.

The Canadian-based Centre for Research on Globalization, a group that advances ideas it feels the “mainstream press” ignores, had an article 4 February 2016 from Dr. Gary Kohls that challenged the linkage theory and said the primary suspect is DTaP,  a common vaccination to prevent whooping cough (along with tetanus and diphtheria).

“In the whole week of reports that I heard or read about, not a single interviewer asked about – and not a single ‘expert’ or mainstream journalists ever mentioned the most likely triggering cause of the epidemic, and that is the neurotoxic, cytotoxic, genotoxic, aluminum that was in every DTaP shot, a vaccine that had been recently mandated (early in 2015) by the Brazilian government to be injected into pregnant women – and therefore into their fetuses,” Kohls wrote.

Brazil began vaccinating pregnant women in late 2014

So is DTaP is the “most likely triggering cause” of microcephaly?

Most of Kohls’ article describes why the Centers for Disease Control and Prevention, pharmaceutical companies and researchers would care to blame the zika virus rather than the vaccine, but its main point is the overlap of the microcephaly incidence and Brazil’s immunization campaign.

Brazil did begin vaccinating pregnant women starting in late 2014. (Hat tip to Brazilian fact-checker Cristina Tardáguila at Lupa News.)However, according to the Brazilian Health Department press release, the vaccine they distributed was a version called Tdap. This was part of an international push to reduce whooping cough in infants. Inoculating mothers late in pregnancy allowed them to pass antibodies to their unborn children.

However, according to the Brazilian Health Department press release, the vaccine they distributed was a version called Tdap. This was part of an international push to reduce whooping cough in infants. Inoculating mothers late in pregnancy allowed them to pass antibodies to their unborn children.

For the rest of this fact-check, we look at Tdap. The Web article named the incorrect vaccine, but if there’s any merit to Kohls’ case — and there isn’t — it lies with the vaccine Brazil used.

Kohl also wrote that “there are 35 other countries across the globe that have confirmed cases of zika virus illness, but none are having any microcephaly reports”.

The European Centre for Disease Prevention and Control does show about that number of countries and territories where zika has been found, but in 13 of those places, there are few cases. Either no instances of zika have been found in the past two months, or the number of cases was less than 10.

So it’s a bit misleading to suggest that the absence of microcephaly disproves the link between the birth defect and the zika virus. If we find more detailed statistics on the number of cases of zika and microcephaly, we’ll update this item, but there’s a much bigger problem with Kohls’ statement.

Evidence on the safety of Tdap

The weakest part of the argument that Tdap plays a role in microcephaly is that  pregnant women in the United States, and elsewhere, have been getting the vaccine and there is no hint of a connection to microcephaly. Elyse Kharbanda is a top national researcher on vaccine safety at HealthPartners Institute for Education and Research in Minneapolis.

“Our research has not shown any link between Tdap vaccination in pregnant women and microcephaly in their children,” Kharbanda told us.

Melissa Brower in the CDC press office reiterated that point.

“Our safety monitoring is continuous,” Brower said. “We have not observed any unusual or unexpected patterns of reporting that would indicate a potential safety problem with maternal Tdap vaccination and microcephaly as a birth outcome.”

A 2015 study published in the peer-reviewed Journal of the American Medical Association included over 29,000 pregnant women in six states. It found no problems of any birth defects for any woman who was vaccinated with Tdap during pregnancy.

Another JAMA study looked at over 26,000 pregnant women in California and reached the same conclusion.

Timing of vaccine important

Researchers at the Vanderbilt Vaccine Research Program further affirm the safety of Tdap. Director and specialist in pediatric infectious diseases Buddy Creech said nothing shows any link between the vaccine and microcephaly or any other birth defect. Creech also noted that the vaccine is given later in pregnancy, between weeks 27 and 36. That timing is important.

“Most organ development and structural changes are occurring in the first trimester,” Creech said. “It’s after the period of most intense organ development, so it removes the question of whether a vaccine caused congenital heart disease, etc.”

However, the CDC says in some cases, microcephaly can occur after the first trimester, so in theory, a vaccination could overlap with the onset of microcephaly. But that doesn’t change the rest of the research pattern.

The United Kingdom launched a vaccination program in 2012, making Tdap available to about 700,000 pregnant women. Researchers looked at the impact on about 20,000 of them and found no increase in pregnancy risks.

On a related note, the New England Journal of Medicine reports that the zika virus was found in the brain tissue of an aborted fetus suffering from microcephaly. While this says nothing about the role of Tdap, it does directly link the zika virus to a particular birth defect.

We contacted the editors at the Centre for Research on Globalization and they said they forwarded our questions to Kohls. If we hear back, we’ll update this item.

Conclusion: Statement is inaccurate in every respect

An online article on the website of the Centre for Research of Globalization said the DTaP vaccine is the mostly likely cause of microcephaly in Brazil. First of all, Brazil used Tdap, a slightly different version of the vaccine. More important, not a bit of evidence supports the assertion that either variety lies behind microcephaly.

Many thousands of pregnant women in the United States and around the world have been getting this vaccine for at least five years and multiple studies have found no ill effects on their babies. a for any birth defect and certainly not microcephaly.

In addition, administering the vaccine later in pregnancy reduces the likelihood that it will interfere with fetal development.

The statement is inaccurate in every respect including naming the wrong version of the vaccine used in Brazil.

This report was originally published by Politifact. See how it appeared there.

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