Covid France: Does receiving different vaccines reduce their efficacy?

Reader Question: When I received my first vaccine doses and booster, I had Pfizer, but when I went for my fourth dose this week I was given Moderna. Will my immune response be reduced because I have received a different vaccine?

People aged 60 and over, immunosuppressed patients and care home residents are now being offered a fourth Covid vaccine dose in France, although this booster remains optional.

Read more: France Covid: fourth vaccine dose now being offered to over-60s

It is not always possible to choose which vaccine you receive when you have additional doses, but scientific studies have shown that mixing vaccines is completely safe.

This is partly because both Pfizer and Moderna are “twin” vaccines, which both use mRNA messenger technology.

Alain Fischer, president of the Conseil d’orientation de la stratégie vaccinale, which advises the government on its vaccination campaign, has previously Tweeted that: “[Moderna] and Pfizer are twin brothers: same efficacy, same safety, same hope of moving on from the health crisis.”

Having different vaccines “does not pose a problem with regards to safety or to efficacy, and it could even give better results,” he has also commented.

The European Medicines Agency and the European Centre for Disease Prevention and Control have expressed similar views.

In December 2021, they published a joint report which found that receiving a different type of vaccine for your booster could indeed elicit a greater immune response than receiving the same vaccine as in previous doses.

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