Covid-19: According to French data, bivalent vaccines do not increase the risk of stroke

When we talk about vaccination, in particular against Covid-19, it’s all about the balance of benefits and risks. However, US health authorities announced in January that they had identified a “signal” regarding a Pfizer-BioNTech vaccine adapted to Omicron BA.4/5. This may lead to an increased risk of stroke in people over 65 years of age compared to the original vaccine, especially if the person was also vaccinated against the flu at the same time. Shortly thereafter, deeper analysis proved encouraging. And the French data published this Wednesday, March 29, is no less important.

In this study, scientists from the Epi-Phare (Health Insurance and National Agency for the Safety of Medicines and Health Products) group followed almost 500,000 people, mostly aged 60 or over, from October 6 to November 9, 2022. 80% of them received the so-called “bivalent” vaccine, that is, aimed at both the original strain of the virus and the Omicron VA.4/5 variant. Therefore, it was he who was suspected of causing more strokes. The rest of the participants were “stung” by the original “monovalent” vaccine, which is no longer in use.

Less than 4000 vaccinated per day

Each of these people was followed up for three weeks after the injection “to adhere to the risk period specified in the original US warning,” points out Mahmoud Zureik, lead author of the study. According to the results, the risk of VKA (whatever it may be) is not higher with the bivalent vaccine than with the parent vaccine. The same goes for the risk of myocardial infarction or pulmonary embolism, always within three weeks of an arm sprain.

Whatever the vaccine, these risks are very low and do not call into question the benefits provided to these most vulnerable people, in particular to protect them from serious forms, according to previous studies. “Our results are encouraging for the continued use of this bivalent vaccine,” the study authors say.

At the end of March, fewer than 4,000 people receive a booster dose of this bivalent vaccine every day, far from the peak reached in mid-December (about 110,000 daily injections). This number may rise again in the fall, when frail people (over 60, people with underlying medical conditions, etc.) will be asked to receive a new reminder. Unless, by then, another vaccine proves more suitable, especially if another option prevails, very different from those currently circulating.