Reinforcement with updated vaccine against Covid reduces the risk of hospitalization by half

The updated booster vaccines have strengthened Americans’ defenses against severe Covid, reducing the risk of hospitalization by 50% compared to groups inoculated with the original ones. The Center for Disease Control and Prevention (CDC) released the data in two studies published last Friday (16).

The research represents the CDC’s first analysis of the performance of reformulated booster vaccines, specially tailored to protect against recent omicron variants, in preventing the serious consequences of infection with the virus, such as hospital admissions.

US health officials are encouraging Americans to get the updated booster vaccines, hoping to inject pep into a vaccination campaign that has been losing steam. But less than a fifth of adults and just a third of people age 65 and older have ever received the updated booster.

New variants of the virus, better able to bypass the immune system, have been gaining ground, and in recent weeks Covid cases and hospitalizations have risen. On average, 375 Americans are dying from Covid each day, a 50% increase over the past two weeks. Older people are especially affected.

The virus intensifies the difficulties of the health system, already pressured by the resurgence of flu and respiratory syncytial virus (RSV), after two years of decline in these infections.

At the same time that federal health officials are encouraging people to test themselves and wear a mask in certain settings, precautions have become much less commonplace in practice. For many infected, it is still difficult to find antiviral drugs for Covid.

“We probably won’t have waves of Covid like we’ve had in the past, which is good. But that doesn’t mean people aren’t still dying, and those lives could be saved if more people took the booster,” says David Dowdy, a researcher at the Johns School. Hopkins Bloomberg for Public Health.

A CDC study released Friday examined how updated boosters protect people from emergency room visits and hospitalizations for Covid in seven health care systems. The study analyzed around 15,000 hospitalizations recorded from mid-September to November, when a good part of the Covid cases were caused by the BA.5 variant of omicron, which is, in part, the target of the updated reinforcements.

But since then, more elusive versions of omicron, known as BQ.1 and BQ.1.1, have become more common, and it’s not clear how relevant the study’s findings are to the newer variants.

During the BA.5 period, people who had received updated boosters were 57% less likely to be hospitalized than unvaccinated people, 38% less likely than people who had recently received doses of the original vaccine, and 45% less than people whose last dose of original vaccine had been taken at least 11 months earlier.

But the CDC study did not look at whether patients had been previously infected with the virus, potentially making the updated vaccines appear less effective than they are. And the survey did not take into account the possibility that certain sectors of the population were more likely to have received drugs such as Paxlovid, which may have influenced the results.

A second study looked at the benefits of upgraded boosters for older Americans at 22 hospitals between early September and late November.

In this population aged 65 years and older, the updated vaccines reduced the risk of hospitalization for Covid by 84% compared to unvaccinated people and by 73% compared to people who received at least two doses of the original vaccines.

CDC scientists said the higher estimates of vaccine efficacy in older people may reflect a variety of differences in the specific groups of patients being studied.