UK: Boosters restore protection vs Omicron

The COVID-19 booster vaccination clearly restores protection against the mild illness caused by the Omicron variant and partially reverses an otherwise sharp decline in vaccine effectiveness, according to the British health authority on Friday.

The first results of a real-world analysis are some of the first data on protection against Omicron outside of laboratory studies that have shown decreased neutralizing activity against Omicron.

"These early estimates should be used with caution, but they suggest that a few months after the second vaccination there is a higher risk of contracting the Omicron variant than the Delta strain," said Dr. Mary Ramsay, Head of Vaccination at UKHSA, adding that protection against serious illness is expected to continue to be higher.

"The data suggest that this risk is significantly reduced after a booster vaccination, so I strongly encourage everyone to get the booster vaccination if it is an option.

In an analysis of 581 people with confirmed Omicron infection, two doses of AstraZeneca (Nasdaq: AZN) or Pfizer-BioNTech vaccines offered significantly less protection against symptomatic infections than against Delta infection.

When boosted with a dose of Pfizer's vaccine (NYSE: PFE), protection from symptomatic infection was about 70% in those who first received AstraZeneca and about 75% in those who received Pfizer.

In comparison, the estimated protection against infection by Delta after a booster is around 90%.

The UKHSA reiterated that Omicron has a growth advantage over Delta and a 3 to 8-fold increased risk of reinfection.

Two UK studies, which have not yet been publicly presented, and three international studies suggested that Omicron produced a 20- to 40-fold reduction in neutralizing antibodies compared to the viruses used to develop vaccines.

The UKHSA stated that while no case of Omicron has resulted in hospitalization or death, there is insufficient data to assess the severity of Omicron.

At current growth rates, Omicron would account for more than 50% of all COVID-19 infections by mid-December, according to the UKHSA, and the number of infections in the UK would exceed one million by the end of the month as new measures come into effect in England, to slow down the spread of Omicron.

"The increasing cases of the Omicron variant, coupled with today's new data, should be a wake-up call for anyone who has not or have not yet received a vaccine," said National Health Service Medical Director Stephen Powis.