A report from South Africa offered a first glimpse of how those vaccinated might fare against the rapidly spreading Omicron variant of the coronavirus.
Laboratory experiments revealed that Omicron appeared to weaken the potency of the Pfizer-BioNTech vaccine, but also hinted that people who received a booster may be better protected.
The study, published online Tuesday, found that the antibodies produced by those vaccinated were much less successful in preventing the Omicron variant from infecting cells than other forms of the coronavirus.
Scientists said the results were somewhat worrying, but there was no reason to panic. The data suggests that those vaccinated could be vulnerable to breakthrough infections with Omicron, which is spreading rapidly in South Africa and has appeared in dozens of countries around the world.
But vaccines stimulate a far-reaching immune response that involves more than just antibodies. These experiments therefore provide an incomplete picture of how the vaccine protects against hospitalization or death from Omicron.
“Although I think there are going to be a lot of infections, I’m not sure it translates into a systems collapse,” Alex Sigal, virologist at the Africa Health Research Institute in Durban, South Africa , who led the research, said in an interview. “I guess it will be under control. “
Dr Sigal and his colleagues have been working at breakneck speed over the past two weeks to develop the virus and then test for antibodies against it. “If I don’t die from the virus, I will die of exhaustion,” he said.
Originally, Dr Sigal was concerned that vaccines would offer no protection. It was possible that the Omicron variant had developed a new way of entering cells, which would have rendered vaccine antibodies useless. “So all our efforts would be garbage,” he said.
Fortunately, this turned out not to be the case.
Dr Sigal and his colleagues used the antibodies of six people who received the Pfizer vaccine without ever having had Covid-19. They also tested the antibodies of six other infected people before receiving the Pfizer vaccine.
The researchers found that the antibodies of all the volunteers behaved less well against Omicron than against an earlier version of the coronavirus. Overall, the potency of their antibodies to Omicron has dropped dramatically, to about a fortieth of the level seen when testing with an earlier version of the virus. This low level of antibodies may not protect against breakthrough Omicron infections.
Theodora Hatziioannou, a virologist at Rockefeller University who was not involved in the research, said the number was not surprising. “It’s more or less what we expected,” she said.
The results could help explain some of the high-profile super-propagation events caused by Omicron. At an office Christmas party in Norway, the virus appears to have infected at least half of the 120 vaccine participants.
Dr. Sigal announcement the results on Twitter Tuesday afternoon.
His team found a clear difference between the two groups of volunteers. The antibodies of the six uninfected vaccinated people were very weak against Omicron. But among the volunteers who had Covid-19 before the vaccination, five out of six were still producing fairly powerful responses.
One of the reasons for this difference is that people vaccinated after infection produce higher levels of antibodies than people who have not been infected.
Dr Sigal said that the experiments won’t say much about how the boosters protect against Omicron until researchers directly test the antibodies of people who have received them. But he suspected that the increased level of antibodies would offer good protection. “The more you have, the better off you will be,” he said.
Kristian Andersen, an infectious disease researcher at the Scripps Research Institute in La Jolla, Calif., Who was not involved in the new study, agreed that the booster shots were likely to help push back the new variant.
“I expect boosters to restore better levels of protection,” he said. “And, most importantly, the first clinical data from South Africa suggests that immunity – whether from vaccines or from previous infections – is still effective in preventing the more severe forms of Covid-19. “
Dr Hatziioannou was less sure of the recalls. She and her colleagues are experimenting with the boosters’ antibodies to test whether they will produce the same robust protection seen in people who received vaccines after infection. “I mean yes, but we have to wait,” she said.
Pfizer and Moderna said they are testing their vaccines against Omicron and will be able to produce vaccines specifically tailored for the variant in about three months.
Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center, said the study reinforced the need to accelerate the development of vaccines specific to Omicron. While there remains some uncertainty as to the extent of the spread of the variant, he said, the best way to restore protection against Omicron will be to give people a vaccine that contains Omicron’s genetic information. .
“Considering the very sharp drop in neutralizing antibody titers observed here with Omicron,” he said, “in my opinion, it would certainly be worth moving forward as quickly as possible in the manufacture of vaccines specific to Omicron. , as long as there seems to be a possibility that it could spread widely.