no, Brazilian microcephaly outbreak was not caused by vaccine

This fact check has been performed based on the information available on the date of publication. Read more about how we work here.

The claim circulates online that the Brazilian microcephaly outbreak, which occurred in 2015, was caused by a vaccine against whooping cough, tetanus and diphtheria. That is not true. Scientific research has shown that the Zika virus, transmitted by infected mosquitoes, was at the origin of the outbreak.

On November 20 post a Twitter user posted an image of a man holding a small-headed baby man. On the photo we read the following text: ‘Brazil: in a few months more than 3000 babies were born with microcephaly, without any scientific evidence the government assumed that the disease was caused by the ‘Zika virus’. Despite this, Australian scientists have now revealed that the true cause of the disease was the toxicity of the mandatory dTPa vaccine, which was administered to pregnant women the previous year. The vaccines were funded by the Bill and Melinda Gates Foundation,” we read (archived here).

Screenshot Twitter

The image is also circulating on Facebook and on Dutch-language Telegram channels (archived here and here).

Microcephaly is a congenital neurological disorder in which the brain does not develop properly. As a result, the skull also remains smaller than normal. In 2015, hundreds of babies were born with microcephaly in the northeastern Brazilian state of Pernambuco. Scientists initially had a guess as to the cause, but investigations showed that the Zika virus was the cause of the outbreak. The virus can cause the so-called ‘Zika fever’. The symptoms are usually mild, but if pregnant women become infected with the virus, the consequences can be more dramatic, including microcephaly. The virus takes its name from the tropical Zika forest in Uganda, where the virus originated.

According to the Facebook post, the outbreak was not caused by the Zika virus, but by the dTPa vaccine, which protects against tetanus, diphtheria and whooping cough. The vaccine is also used in Belgium. The Agency for Care and Health recommends starting the vaccination when babies are eight weeks old. They then receive a booster vaccination when they are 15 months old and another when they are five to six years old. The dTPa vaccine is also administered again at the age of fourteen, and then again in adulthood. In addition, the Agency recommends a booster injection for women who are between 24 and 32 weeks pregnant.

Is the dTPa vaccine at the root of Brazil’s 2015 microcephaly outbreak?

We contact internist Steven Van Den Broucke, who is an infectious disease specialist at the Institute of Tropical Medicine. Van Den Broucke: ‘Scientists have conducted a great deal of epidemiological research to find out what caused the microcephaly outbreak in Pernambuco. Scientists discovered that a major Zika epidemic had taken place a few months earlier. The dengue virus was also one of the suspects, but the number of dengue infections was rather low.’

‘The link with the dTPa vaccine has been investigated, as has the link with other toxins,’ says Van Den Broucke. ‘But scientific research published in 2017 in the scientific journal The Lancet is clear: the only causal link that has been found is with the Zika virus.’

We also read that in the study conclusion: ‘The association between microcephaly and congenital Zika virus infection was confirmed. We provide evidence of the absence of an effect of other potential factors, such as exposure to pyriproxyfen or vaccines (…) during pregnancy. We thus confirm the findings of an ecological study of pyriproxyfen in Pernambuco and previous studies on the safety of dTPa vaccine administration during pregnancy.’

Screenshot The Lancet

Bill & Melinda Gates Foundation

The image also states that the Bill & Melinda Gates Foundation allegedly funded the dTPa vaccines. That’s not right either. The foundation previously did research into vaccines against diphtheria and tetanus and funded research into the effect of the dTPa vaccine on pregnant women, but not in Brazil. This was confirmed by a spokesperson for the foundation to the Australian news agency AAP.

It is no coincidence that the Facebook image refers to the Bill & Melinda Gates Foundation. Gates is often the target of conspiracy theorists. Knack has also written several fact checks (see here and here) about Gates.


The claim circulates online that the Brazilian microcephaly outbreak, which occurred in 2015, was caused by a vaccine against whooping cough, tetanus and diphtheria. That is not true. Scientific research has shown that the Zika virus, transmitted by infected mosquitoes, was at the origin of the outbreak. We therefore assess that the microcephaly outbreak in Brazil was caused by the dTPa vaccine as untrue.

Climate warming

The Zika virus is mainly spread by the dengue mosquito (Aedis Aegypti). ‘The mosquito is a very effective carrier of various tropical viruses, such as yellow fever, dengue and Zika,’ says Steven Van Den Broucke (Tropical Institute). The dengue mosquito is mainly found in tropical regions.

The Asian tiger mosquito can also transmit tropical viruses such as yellow fever and dengue. This mosquito also occurs in temperate climate zones. ‘The Asian tiger mosquito has already been found in our country, albeit without viruses,’ says Van Den Broucke. ‘Specimen with the viruses have been found in the United States and southern Europe. If the climate continues to warm up, it is very likely that the mosquito will spread further in temperate regions.’

The fear that tropical viruses will eventually also gain a foothold in Europe is real, says Van Den Broucke. ‘It is not impossible that we will suddenly find a mosquito in our region that is infected with yellow fever or dengue, for example. It is an evolution that we must keep an eye on.’


In the article you will find links to all sources used.

In addition, the following people were contacted for this fact check:

– Telephone interview with Steven Van Den Broucke on November 25, 2022.

All sources were last consulted on November 30, 2022.


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