The first real-world study of how vaccines resist the Omicron variant showed a significant drop in protection against symptomatic cases caused by the new, rapidly spreading form of the coronavirus.
But the study, released by UK government scientists on Friday, also indicated that the third doses of the vaccine offered considerable defense against Omicron.
Government scientists on Friday also offered the most complete look to date how quickly Omicron was spreading through England’s highly vaccinated population, warning that the variant could overtake Delta by mid-December and, without any precautionary measures, skyrocket Covid-19 cases.
These warnings were reinforced by a England computer modeling study released on Saturday suggesting that even in populations with high levels of immunity, Omicron could dramatically disrupt life and overwhelm hospitals. Scientists have warned that those projections may change as they learn more about the severity of Omicron infections.
The vaccine study released on Friday indicated reduced levels of protection. Four months after people received a second dose of the Pfizer-BioNTech vaccine, the injections were about 35% effective in preventing symptomatic infections caused by Omicron, a significant drop in their performance against the Delta variant, the scientists found. .
A third dose of the Pfizer-BioNTech vaccine, however, brought the figure to around 75 percent.
Two doses of AstraZeneca vaccine appeared to offer virtually no protection against symptomatic infection caused by Omicron several months after vaccination. But for those recipients, an extra dose of Pfizer-BioNTech paid big dividends, increasing the efficacy against the variant to 71%.
Still, the study’s authors said they expected vaccines to remain a bulwark against hospitalizations and deaths, and even infections, caused by Omicron. And the researchers warned that even in a country following the variant as closely as Britain, it was too early to know precisely how well the vaccines would work.
This study was published with new findings on how easily Omicron manages to spread. A person infected with the Omicron variant, for example, is about three times more likely than a person infected with the Delta variant to pass the virus on to other family members, the UK Health Security Agency reported.
And close contact from an Omicron case is about twice as likely as close contact from a person infected with Delta to catch the virus.
Neil Ferguson, an epidemiologist at Imperial College London, said Omicron’s ability to evade the body’s immune defenses was most of its advantage over previous variants. But the modeling work of his research team also suggested that Omicron was simply more contagious than Delta, by around 25 to 50 percent.
“I think there’s a significant amount of immune evasion,” Dr Ferguson said, referring to the virus’s ability to dodge the body’s defenses. “But it’s also more inherently transmissible than Delta.”
He and other scientists have warned that evidence is still coming in and better monitoring in places where the Omicron wave is most advanced could affect their findings.
The World Health Organization said this week that some evidence had emerged that Omicron caused milder illness than Delta, but it was too early to be sure. Still, scientists have warned that if the variant continues to spread as quickly as in England, where cases double every 2.5 days, healthcare systems around the world could be inundated with patients.
Even though Omicron causes serious illness at only half the rate of the Delta variant, Dr Ferguson said, his computer modeling suggested 5,000 people could be admitted to hospitals across Britain daily at the height of its Omicron wave. – a figure higher than anything that has been seen. at any other time during the pandemic.
Scientists said widespread vaccination in countries like Britain and the United States would prevent as many people from dying as in previous waves. But experts also warned that patients with Covid and other illnesses would suffer if hospitals became too full.
“It only takes a small dip in protection against critical illness for these very large numbers of infections to translate into levels of hospitalization that we cannot cope with,” said Dr Ferguson.
It will take several weeks to understand how the current outbreak of Omicron infections can translate into hospital care. “I’m afraid by the time we know gravity,” said Dr Ferguson, “it may be too late to act.”
The potential for an increase in hospitalizations was highlighted by the modeling study released on Saturday, created by a separate group of experts from the London School of Hygiene & Tropical Medicine. For now, these scientists have speculated that Omicron would cause a disease as severe as Delta in unvaccinated people, but also that increasing levels of immunity from previous vaccinations and infections would dampen the Omicron wave, as has happened. is produced in South Africa.
In the most likely scenario some outside experts say – in which Omicron has largely escaped people’s immune defenses, but the booster doses have also proven to be very effective – scientists have said England could be hit hard. . As of April, they predicted around 300,000 hospitalizations and 47,000 deaths.
This could place a greater daily burden on English hospitals at the peak of the Omicron wave than has been seen at any time earlier in the pandemic.
Importantly, scientists have said that reintroducing certain restrictions could save thousands of lives and spare tens of thousands of hospital stays.
External experts stressed that Omicron remains poorly understood, that people may be able to fight serious infections more effectively than models predicted, and that the arrival of new antiviral pills in the coming months may ease the blow. infections.
Still, scientists have urged governments to speed up vaccination campaigns, share doses with least-vaccinated countries, and consider measures such as more self-tests or even further restrictions.
“The coronavirus is not done with us,” said Michael Head, senior researcher in global health at the University of Southampton in England.
“A tactic of ‘turning off the lights and pretending we’re not there’ is a failed policy.”