The European Medicines Agency (EMA) on Friday said it was too early to determine whether more than the two shots that are currently required for most approved Covid-19 vaccines would be called for, saying it was confident for now that the established regimen was sufficient.
Pfizer and partner BioNTech have unveiled plans to ask European and US regulators to authorise a booster dose following its two-shot regimen, based on evidence of greater risk of infection six months after inoculation and the spread of the highly contagious Delta variant.
The World Health Organisation (WHO) also said on Friday that it was not clear if booster vaccines will be needed to maintain protection until further data is collected.
"We don’t know whether booster vaccines will be needed to maintain protection against Covid-19 until additional data is collected, but the question is under consideration by researchers," the WHO said in a reply to a Reuters query.
"There is limited data available on how long protection from current Covid-19 vaccine doses lasts and whether an additional booster dose would be beneficial and for whom," it said.
New vaccine side effects
Meanwhile, the EMA also on Friday recommended adding heart inflammation as a possible side effect of mRNA vaccines from Pfizer and Moderna, and advised people with a history of a rare blood disorder to avoid getting Johnson & Johnson's coronavirus shot.
The safety committee of Europe's drug regulator said heart conditions myocarditis and pericarditis must be listed as possible side effects of the two mRNA vaccines.
Such cases primarily occurred within 14 days from vaccination, more often after the second dose and in younger adult men, the EMA said. This is in line with findings from US health officials last month.
The EMA panel also recommended that people who have a history of capillary leak syndrome (CLS) must not be vaccinated with J&J's single-shot vaccine. The watchdog in June asked CLS to be added as a side effect from AstraZeneca's shot.
The EMA also recommended adding a warning for Guillain-Barre syndrome to the AstraZeneca vaccine.
Both AstraZeneca and J&J vaccines use different versions of a cold virus to deliver instructions for making coronavirus proteins to produce an immune response.