WHO experts warn against combining Covid-19 vaccines

In the middle of the global concern over new variants of Covid-19, experts from the World Health Organization (WHO) warn against combining vaccines after Canada and Thailand clear their use. On the other hand, the Argentine government had started to analyze this alternative, to face the potential lack of second doses of certain vaccines.

“It’s a bit of a dangerous trend here. We’re in an area with no data or evidence when it comes to mixing and matching.”said the doctor this Monday Soumya Swaminathan, WHO Chief Scientist during a virtual conference. Thus, the experts of the international organization ensure that few data are available regarding the health consequences by mixing the doses of different inoculants against the coronavirus.

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“It will be a chaotic situation in countries if citizens start to decide when and who to take a second, third and fourth dose,” added the WHO expert, from where they insist that Data from combined studies of different vaccines regarding immunogenicity and safety are still pending and have yet to be evaluated.

As part of the research process around the combination of vaccines in different countries, including Argentina, WHO warning comes especially after Thailand and Canada say they will continue the practice to mix doses from different laboratories.

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Amid an escalation in coronavirus infections derived from the Delta variant, Thailand combine vaccines AstraZeneca Yes Sinovac for health workers, despite WHO warnings. Authorities noted that mThey will mix a first dose of the Chinese Sinovac vaccine with a second dose of AstraZeneca for a “boost” effect in six weeks instead of 12.

In this way the Thailand’s Chief Virologist Yong Poovorawan, indicated that this is possible since an inoculant based on an inactivated virus (Sinovac) is combined with a viral vaccine (AstraZeneca). For his part, the specialist responded to criticism from the WHO since “They cannot wait for the 12 weeks necessary for the booster”, but that “in the future, if there are better vaccines (…) we will find a better way to manage the situation”.

The Southeast Asian nation is one of the hardest hit by the coronavirus and its government has received countless criticism for its handling of the pandemic. In addition, it has a weak health system and records on average 6,695 new cases per day. Cases are up 162% from June 11 a month ago.

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On another side, Canada he also announced last June that citizens who receive the first dose of AstraZeneca will be able to receive the Pfizer-BioNTech or Moderna vaccine for the second dose.

“New evidence is starting to emerge suggesting that immune responses are better when a first dose of AstraZeneca vaccine is followed by mRNA vaccine as the second dose,” said Shelley Deeks, MD, vice president. Canada’s National Advisory Committee on Immunization. Pfizer and Moderna vaccines are the two available vaccines that use mRNA technology.

Meanwhile, the committee noted that people at high risk of exposure to Covid-19 or serious illness might choose to get AstraZeneca rather than wait for Pfizer or Moderna.

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