This study shows that overall levels of antibodies that can prevent virus infection in the lab are greater following two doses of the Pfizer vaccine than with two doses of the AZ vaccine, and this is especially noticeable for some viral variants that are in circulation.

It isn’t clear if these lower antibody levels are due to differences in the vaccine delivery system – where AZ use a chimpanzee adenovirus and Pfizer uses mRNA – or in the form of the coronavirus spike protein used to raise immunity.

What this type of laboratory study doesn’t tell us is how well vaccine immunity is continuing to protect people from serious disease and death. There’s more to immunity than simply high levels of virus-killing antibodies, and it may well be that as far as protection against serious disease is concerned, there is still a lot of immunity left in the tank. So far, the evidence suggests that, in most people, the vaccines are continuing to perform well.

But that doesn’t mean we should be complacent. We should continue to monitor vaccine effectiveness, especially against existing and new variants that will undoubtedly arise in future.

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