Vaccine manufacturers will increasingly have to adjust vaccines due to the new coronavirus variants that have emerged, the head of the World Health Organization (WHO) warned on Monday.
Dr Tedros Adhanom Ghebreyesus said that the emergence of mutated versions of the virus had "raised questions" about their impact on vaccines particularly after South Africa decided to halt AstraZeneca vaccinations when a study showed the vaccine was less effective at preventing the variant there.
"This is clearly concerning news," said Dr Tedros at a press conference on Monday, while emphasising that there were "important caveats" to the vaccine study such as the younger age of participants.
It remains to be seen whether the AstraZeneca/Oxford COVID vaccine prevents severe disease in those infected with the South African variant.
But, Dr Tedros warned, it serves as a reminder that people need to reduce spread of the virus through physical distancing and hand washing.
"Every time you decide to stay at home, to avoid crowds, to wear a mask, or to clean your hands you're denying the virus the opportunity to spread and the opportunity to change in ways that could make vaccines less effective," he said.
Experts have said that although the coronavirus does not mutate as frequently as the flu, the more it spreads, the more opportunities it has to mutate.
But he compared the COVID vaccines to flu vaccines nonetheless, stating that future jabs and boosters would have to be adjusted.
"This is what happens with flu vaccines which are updated twice a year to match the dominant strains," Dr Tedros said.
Dr Salim Abdool Karim, the co-chair of South Africa's coronavirus ministerial advisory committee, said that the Pfizer and Sinopharm COVID vaccines had "minimal reduction" in the antibodies but that for the AstraZeneca vaccine there were "very substantial reductions" in neutralising the virus.
Dr Karim said they were considering rolling out the AstraZeneca vaccine in 100,000 individuals so they can monitor hospitalisations. If the vaccine is effective in preventing hospitalisations, then they could inoculate more people.
"We don't want to end up with a situation where we've vaccinated a million people or two million people for a vaccine that may not be effective at preventing hospitalisation and severe disease," he said.