Covid-19 Vaccine Booster Shot Cuts Omicron Death Risk by 95%, UK Study Shows

The highly mutated Omicron variant can easily evade immune defenses to infect vaccinated people, leading to record-high case numbers across the world as the variant spread, even in highly-vaccinated places like the UK But several studies have shown that boosting restores some protection against symptomatic illness and, to a greater degree, against hospitalization.

The latest data show that protection is greater still against death.

The analysis didn’t adjust for age but was only done for those 50 and older. That is the population at highest risk of severe illness and death and also the age group most likely to have received a booster shot. Britain’s booster campaign mostly used the shots made by

Pfizer Inc.

and

Moderna Inc.,

even in those who received the

Astra Zeneca

PLC vaccinate for their first two doses.

In its latest report, UKHSA said that vaccine effectiveness against death after two shots fell from more than 90% during the Delta wave to around 60% during the Omicron surge. A booster shot increased protection against death from Omicron to around 95%.

More than 37 million people in the UK have received a booster shot, over 64% of people aged 12 and over.

The data suggests that immunity from vaccination plays a key role in keeping a lid on the number of people who have become severely ill with Covid-19, despite record-high case numbers. What is more, among those who are admitted to hospitals, the proportion of cases going on to develop the most severe illness, requiring mechanical ventilationhas been lower than in earlier waves.

Vaccine makers are meanwhile racing to test Omicron-specific vaccines. Pfizer and Moderna both recently started clinical trials for versions of their vaccines that have been adapted for the new variant. It isn’t known whether variant shots will be needed, given that boosters using the original vaccines have been shown to shore up immunity. But the manufacturers say they are preparing to make variant shots available if authorities deem them necessary, and they prove safe and effective.

Also likely contributing to lower levels of severe disease are immunity from prior infection, treatments that prevent disease progression and the variant itself, which appears to cause milder symptoms than Delta. A December study from Imperial College London suggests that someone who had neither been vaccinated nor previously infected was 10% to 11% less likely to be hospitalized with the Omicron variant than with Delta.

Although Omicron is less likely to lead to severe disease than earlier variants, sky-high case numbers mean that deaths have nonetheless increased during the Omicron wave. Around 246 people died with Covid-19 every day in the UK over the past week.

That is the highest in nearly a year, but still a fraction of last winter’s peak of 1,286. And while Covid-19 wasn’t the main cause of death in all of those people, it was still the dominant cause for most of them. Death certificate data from the UK’s Office for National Statistics show that the virus was the underlying cause in around three-quarters of all deaths with Covid-19 in England in the week ending Jan. 14.

Write to Denise Roland at [email protected]