Good timing is the key to success – even for breaking out of an Omicron wave. Research from Japan suggests that a breakthrough SARS-CoV-2 infection months later after COVID-19 vaccination provides greater protection against the Omicron type than close-distance vaccination and infection.1,
This finding implies that countries that saw a large number of non-Omicron infections at the end of 2021 have an advantage in coming up with a new version of 2022. The study has not yet been peer reviewed.
The population of many countries has gained immunity through a combination of different types of vaccinations and infections. But the population of Japan is mainly protected by vaccination with mRNA vaccines. Study co-author Takeshi Arashiro, an infectious disease researcher at Japan’s National Institute of Infectious Diseases in Tokyo, and his colleagues wanted to understand whether the country’s mostly single-source immunity would leave the population particularly susceptible to Omicron. . So far, there have been few success cases in the country, but “we fear that once the Omicron variant is in high transmission in Japan, we may see an entirely different picture”, Arashiro says.
The team collected antibodies from people in Japan who had received two doses of the Pfizer-BioNtech COVID-19 vaccine and later became infected with either the alpha or delta version. The researchers tested the ability of these antibodies to protect cultured cells from SARS-CoV-2 infection, and found that the length of time between a person’s vaccination and successful infection was closely related to whether the person’s antibodies were infected. How do cells protect against – specifically omicrons.
“This is an interesting study,” says immunologist Jenna Guthmiller at the University of Chicago in Illinois. She cautions that the results are completely correlated, but adds that they are in line with immunologists’ general understanding of how antibody responses mature over time.
Guthmiller explains that vaccination causes an emergency burst of antibody production, as would a natural infection. If a person becomes infected soon after vaccination, these antibodies are probably still circulating in the blood, where they will attach to the virus and kill it quickly.
But when a person becomes infected months after vaccination, the antibodies that respond come from a new and improved batch made by long-lived cells that carry the pathogen’s memory. When the body encounters the pathogen again, these memory cells are called back on duty and have a chance to refine antibodies, providing better protection against subsequent infections.
booster vs success
Guthmiller says she would like to see similar data focused on vaccine boosters rather than breakthrough infections. “Does the time between your first two doses and then your booster affect how many cross-reactive antibodies you have?” He asked.
Arashiro and his colleagues haven’t investigated it, but they think the booster is still Japan’s best bet for countering the Omicron wave. “We are trying to push for booster doses as soon as possible – especially among vulnerable populations – because we are only protected by vaccines, not natural infections,” he says.