The rate of severe infection with Covid-19 in the fourth week after the fourth dose of the vaccine was lower than in those who received only three doses at a rate of 3.5. However, protection against serious illness did not appear to decrease in the six weeks after the fourth dose, although the study period was not long enough to determine exactly how long this protection lasted. The rate of confirmed infection in the fourth week after the fourth dose was lower than in the group of three doses by a factor of 2. There seemed to be maximum protection against Omicron in the fourth week after vaccination, but the rate decreased to 1.1 by the eighth week, suggesting that “protection against confirmed infection is rapidly weakening,” the study says. The protection provided by any vaccine is naturally reduced, but a vaccine activates the immune system to produce protective antibodies if it encounters threats later. The currently available Covid-19 vaccines were developed to protect against the original strain of the virus. Omicron is significantly different, and as a result, vaccines have lost some of their effectiveness. Israel and the United States are among the governments that have proposed fourth vaccines for some people at high risk of serious illness, such as the elderly. Last week, the FDA extended its emergency authorization to allow adults 50 and older to get a second booster vaccine just four months after the first Pfizer or Moderna booster vaccines. People with certain immune deficiencies may also receive a fourth dose in the United States. But the debate continues over whether it is needed for the general population. The US Food and Drug Administration’s Independent Vaccine Committee meets Wednesday to discuss what the country’s support strategy should go. Some experts have suggested that the Covid-19 vaccine could become an annual vaccine like the flu vaccine. There are limits to what new research may say about the need for a fourth dose of vaccine. It only compares the protection provided by the third and fourth doses, so it does not include unvaccinated individuals for comparison. It also does not add to the debate over whether people under the age of 60 may need a fourth dose. Previous research in Israel has shown that the fourth dose did not do much in younger healthy populations, at least in terms of protection against infection. For a confirmed infection, “a fourth dose appears to provide only short-term protection and a moderate absolute benefit,” the researchers wrote. But when it comes to serious infection, the fourth shot seems to help. “Overall, these assays provide evidence of the effectiveness of a fourth dose of vaccine against a serious illness caused by the Omicron variant compared to a third dose given more than four months later,” the study said. Even with this news, it is not clear how many eligible people will receive a fourth vaccine for Covid-19. About 66% of the US population has had at least one vaccine for Covid-19, but only 30% of people are fully vaccinated with a booster dose, according to the US Centers for Disease Control and Prevention.
