The European Union's drugs regulator said it could make sense to administer Covid-19 vaccine boosters as early as three months after the initial two-shot regimen amid "extremely worrying" infection numbers in the region.
"While the current recommendation is to administer boosters preferably after six months, the data currently available support safe and effective administration of a booster as early as three months from completion," the European Medicines Agency's (EMA) Head of Vaccines Strategy, Dr Marco Cavaleri, told a media briefing.
Preparations were in full swing for the review of any redesigned vaccines that target the new Omicron variant, should it be needed, but the spread of the dominant Delta variant should for now be front and centre of the fight against the current wave, he said.
"The immunological situation remains extremely worrying in Europe," Dr Cavaleri said.
"(Delta) will remain the main focus of public health actions to cope with the pandemic and its consequences." he added.
The EMA executive said vaccine makers were required to submit results of laboratory tests to determine the level of neutralising antibodies generated by their shots against Omicron, part of the fact-finding to determine the need for vaccine upgrades.
Pfizer and BioNTech yesterday became the first vaccine developers to publish such data, saying a three-shot course of their vaccine was able to neutralise Omicron.
Dr Cavaleri also said that so far no safety concerns have emerged from the vaccination campaign among five to 11-year-old children in the United States, where more than 5 million in that age group have received at least one shot.
WHO recommends boosters for certain groups
The World Health Organization's vaccine advisory panel has recommended that people who are immunocompromised or received an inactivated vaccine should receive a booster dose of a Covid-19 shot.
Many countries have been rolling out booster shots, targeting the elderly and people with underlying health issues, but worries about the new Omicron variant have prompted some to expand their use to larger portions of their populations.
With vaccination rates worryingly low in much of the developing world, the WHO has said in recent months that administering primary doses - rather than boosters - should be a priority.
The recommendation comes after the Strategic Advisory Group of Experts (SAGE) on immunisation held a meeting on Tuesday to evaluate the need for Covid-19 boosters.
Speaking in a briefing, SAGE chair Alejandro Cravioto said emerging data showed that vaccines' efficacy against Covid-19 wanes, with a significant decline seen in older people in particular.
Covid-19 vaccines protect "very well" through six months after the last dose with some "minor, modest reduction" in protection, Kate O'Brien, director of the WHO's immunisation department, said.
Inactivated vaccines which take the SARS-CoV-2 virus and inactivate or kill it using chemicals, heat or radiation, are made by Chinese manufacturers Sinovac Biotech, state-owned Sinopharm and India's Bharat Biotech.
A single dose of the Johnson & Johnson (Janssen) vaccine is still effective, but data from the company's clinical trials using two doses clearly show the benefit of having further vaccination, Dr Cravioto said.
Dr O'Brien also said that wealthy countries may start to hoard Covid-19 vaccines again, threatening global supplies as they seek to shore up stocks to fight the new Omicron variant.
