Europe: The protection against the COVID-19 infection offered by the vaccines wears off rapidly, especially against symptomatic disease with the Omicron variant, a study conducted by the Sciensano public health institute shows.
Protection against hospitalization remains stable.
The researchers analysed the test results, vaccination status as well as health care centre admissions of 1.5 million Belgian residents between July 2021 and April 2022, when Belgium dealt with the Delta and Omicron variants.
The Sciensano study came to an end, “The Covid-19 vaccines used in the Belgian vaccination campaign provide good protection against hospitalization for Covid-19 infection with the Omicron variant, and lower protection against symptomatic infection.”
“Although protection decreases several months after vaccination, protection against hospitalization increases to 87% after booster vaccination.”
Information from 1,433,135 individuals was analysed to calculate the protection rate against symptomatic infection, falling slightly ill as a result of a COVID disease, as well as data from 662,220 people to calculate the rate against hospitalizations.
Moreover, those who received the first two doses, the so-called primary or essential vaccination, were initially 81 percent more protected against symptomatic Delta infection than the unvaccinated people.
After 100 to 150 days, three to five months, this percentage has been decreased by 56 percent. After a booster dose, which has been increased back to 84 percent.
It was impossible to ascertain how long the protection from the booster shot lasted against Delta because the extra doses were only administered when the variant had almost disappeared in Belgium.
In addition, for the protection against the Omicron variant, the results are even more striking. After the first two shots, the initial protection against symptomatic infection was just 37 percent. This was halved after three to five months.
Furthermore, the booster shot surpassed the initial protection of 52 percent but appeared to wear off after a few months of 25 percent. “This has to do with the characteristics of Omicron.
It escapes the human body’s immune system more quickly than, for example, a Delta or Alpha variant,” Sciensano researcher Joris van Loenhout shared the information.