European Union regulators have warned that frequent COVID-19 booster shots could adversely affect the immune system and might not be feasible. Repeat booster doses every four months could eventually weaken the immune system and tire out people, according to the European Medicines Agency (EMA).
Instead, countries should leave more time between booster programmes and tie them to the onset of the cold season in each hemisphere, following the blueprint set out by influenza vaccination strategies, the agency said.
Bloomberg reports that the advice coincides with some countries considering the possibility of offering second booster shots, to provide further protection against surging Omicron infections. Earlier this month Israel became the first nation to start administering a second booster, or fourth shot, to those over 60.
The UK has said boosters are providing good levels of protection and there is no need for a second booster shot at the moment.
Boosters “can be done once, or maybe twice, but itʼs not something we think should be repeated constantly”, said Marco Cavaleri, the EMA head of biological health threats and vaccines strategy, on Tuesday (11 January). “We need to think about how we can transition from the current pandemic setting to a more endemic setting.”
The EU regulator also said that oral and intravenous antivirals, such as Paxlovid and Remdesivir, maintain their efficacy against Omicron. The agency said that April is the soonest it could approve a new vaccine targeting a specific variant, as the process takes about three to four months.
The World Health Organization (WHO) has also warned that repeating booster doses of the original COVID vaccines is not a viable strategy against emerging variants.
The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-Co-VAC) said: “A vaccination strategy based on repeated booster doses of the original vaccine composition is unlikely to be appropriate or sustainable. COVID-19 vaccines that have high impact on prevention of infection and transmission, in addition to the prevention of severe disease and death, are needed and should be developed.”
The group said there could be a need to update the existing vaccines to better target emerging variants such as Omicron, and called for the development of new jabs that not only protect people, who contract COVID, against falling seriously ill but also better prevent them from catching the virus in the first place.
It also suggested that vaccine developers should strive to create jabs that “elicit immune responses that are broad, strong, and long-lasting, to reduce the need for successive booster doses”.
Until new vaccines have been developed, the group said, “the composition of current COVID-19 vaccines may need to be updated”.
According to the WHO, 331 candidate vaccines are currently being worked on around the world.
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