THE United States (US) Food and Drug Administration (FDA) is preparing to allow “mix and match” Covid-19 vaccine boosting, in which people will get a different additional jab to the dose they initially received, reported US media.

The FDA may make the announcement tomorrow, when it is also expected to authorise boosters for the Moderna and Johnson & Johnson vaccines, said the New York Times, citing sources familiar with the situation.

A preliminary study released in the US last week showed that people who have received the J&J vaccine may benefit from a booster dose of a different, messenger-RNA vaccine such as Pfizer or Moderna.

But multiple reports quoted people familiar with the discussions as saying one shot may not be recommended over another, and the FDA may say using the same vaccine is preferable when possible.

“People should generally get the same vaccine as their initial series,” a federal official told the Washington Post.

Proponents of mixing and matching point to its benefits in terms of simplifying vaccine roll-out, and ensuring those who need boosters can get them regardless of which jab they initially had.

“From a public health perspective, there is a clear need in some situations for individuals to receive a different vaccine,” Amanda Cohn, a high-ranking Disease Control and Prevention Centres official, told the New York Times.

In July, World Health Organisation (WHO) chief scientist Soumya Swaminathan said mixing and matching vaccines is “a bit of a data-free, evidence-free zone”.

The US study on boosters, which has not yet been peer-reviewed, has several limitations.

The number of participants is small and the immune response can evolve beyond the 15 days observed during the study.

In the US, over-65s, adults with high-risk medical conditions, and those in jobs frequently exposed to the virus are eligible to receive booster shots.

WHO vaccine advisers had last week recommended people with weakened immune systems be offered an additional dose of all WHO-approved Covid-19 vaccines.

But WHO wants a moratorium on booster doses for the general population until the end of the year, to prioritise first doses in the dozens of nations starved of vaccines. – AFP, October 19, 2021.