AstraZeneca’s COVID-19 vaccine does much more than prevent people from becoming seriously ill: it appears to reduce the transmission of the virus and offers strong protection for three months with just a single dose, researchers said in an encouraging twist the campaign to suppress the outbreak.
Preliminary findings from Oxford University, co-developer of the vaccine, could vindicate the British government’s controversial strategy of delaying the second shot by up to 12 weeks so that a first dose can be given quickly to more people. So far, the recommended time between doses has been four weeks.
Research could also bring scientists closer to one of the big questions about the impetus for vaccination: will vaccines really slow the spread of coronavirus?
It is unclear what implications, if any, the findings might have for the other two major vaccines used in the West, Pfizer and Moderna.
In the United States, Dr. Anthony Fauci, the nation’s top infectious disease expert, dismissed the idea of deliberately delaying the second shots, saying the U.S. will “follow science” and data from clinical trials. The two doses of Pifzer and Moderna vaccines are supposed to be given between three and four weeks apart.
Still, the research seems like good news in the desperate effort to stop the spread of the virus and also suggests a way to alleviate vaccine shortages and get more arms shots faster.
The manufacturers of the three vaccines have said their vaccines were found to be 70% to 95% effective in clinical trials to protect people from diseases caused by the virus. But it was unclear whether vaccines could also suppress the transmission of the virus, that is, whether someone inoculated could acquire the virus without becoming ill and spread it to other people.
As a result, experts have said that even vaccinated people should continue to wear masks and keep their distance from others.
The Oxford study, however, found that the vaccine not only prevented serious disease, but appeared to reduce the transmission of the virus by two-thirds. The study has not yet been peer-reviewed.
Study volunteers were given regular nasal swabs. The level of swabs positive for the virus, both those with COVID-19 symptoms and those without any, was 67% lower in the vaccinated group.
“This must have a really beneficial effect on transmission,” Oxford principal investigator Sarah Gilbert said at a meeting of the New York Academy of Sciences.
The researchers also examined the likelihood that vaccinated people would suffer from a symptom-free infection. In a subset of volunteers, there were 16 asymptomatic infections among the vaccinated and 31 in an unvaccinated comparison group.
Pfizer and Moderna are also studying the effect of their vaccines on asymptomatic infections.
Only Pfizer and Moderna vaccines are used in the United States. Britain uses both AstraZeneca and Pfizer. AstraZeneca’s has also been authorized by the European Union of 27 countries. Pfizer has not approved the British government’s decision to extend the time between doses.
Mene Pangalos, executive vice president of research and development for biopharmaceuticals at AstraZeneca, said no patient experienced severe COVID-19 or needed hospitalization three weeks after receiving a first dose and that efficacy appeared to increase to 12 weeks. after the initial vaccination.
“Our data suggest you want to be as close to 12 weeks as you can” for the second dose, Pangalos said.
British Health Secretary Matt Hancock said the study “supports the strategy we have adopted” to make sure more people get at least one shot. Britain’s decision has been criticized as risky by other European countries.
Stephen Evans, of the London School of Hygiene and Tropical Medicine, said the study’s suggestion that a single dose protect people for 12 weeks was “useful, but not definitive.”
He said the same authors acknowledged that their research was not designed to investigate the vaccine dosing schedule and that their findings were based on statistical models, not on actual patients tracked over time.
“There is certainly no very solid evidence, but there are also no indications that this is wrong,” Evans said of Britain’s strategy.
One of the Oxford researchers, Dr Andrew Pollard, said scientists also believe the AstraZeneca vaccine will continue to offer protection against new variants of COVID-19, although they are still waiting for data on this. Fast-spreading mutant versions have caused alarms around the world.
“If we need to upgrade vaccines, it’s actually a relatively simple process. It only takes a matter of months, instead of the huge efforts everyone made last year to conduct the large-scale trials,” Pollard told the BBC.
Meanwhile, a UN-backed program to supply COVID-19 vaccines to the world’s most needy people is being prepared after a troubled start. The COVAX center on Wednesday announced plans for an initial distribution of about 100 million doses by the end of March and more than 200 million more by the end of June in dozens of countries.
Almost all the doses planned for the first phase will have to come from AstraZeneca and its partner, the Serum Institute of India. Deployment will depend on the World Health Organization authorizing the firing of AstraZeneca for emergency use, which is expected to happen this month.
About 190 countries and territories are participating in COVAX, which has seen rich nations take over the supply of vaccines, sometimes at premium prices.
The global death toll from the pandemic has exceeded 2.2 million, including some 447,000 in the U.S., according to data from Johns Hopkins University.
New cases a day in the U.S. and the number of Americans in the hospital with COVID-19 have dropped dramatically in recent weeks, but deaths remain almost at an all-time high, averaging about 3,100 a day. Deaths are often left behind the infection curve, because it can take weeks to get sick and die from COVID-19.
As the Super Bowl approaches, Fauci warns people not to invite other people to Super Bowl parties, and urges viewers to “relax and cool off” to avoid turning Sunday’s big game into a super outreach event.
“You don’t want parties with people you don’t have too much contact with,” he told NBC’s “Today” program. “You just don’t know if they are infected.”
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Associated Press reporters Jill Lawless, Maria Cheng, Jamey Keaten and Ricardo Alonso-Zaldivar contributed to this report.
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