A growing body of evidence suggests that vaccination and natural immunity lead to particularly robust protection against the virus variants, for those who have postponed being vaccinated because they have already been infected with the coronavirus.
Hybrid immunity is a natural immunity from infection combined with vaccine immunity and it appears to be more protective than just infection or vaccination.
Why Should People Still Be Vaccinated Who Have Covid?
“The immunity of people who have previously been infected really increases dramatically if they get at least one dose of vaccine,” said Shane Crotty, a professor of immunology at California’s La Jolla Institute of Immunology.
Fikadu Tafesse, an Oregon University of Health and Science associate professor for molecular microbiology and immunology agreed. Tafesse investigations have found vaccination leading to increased levels of antibody neutralization in people previously infected with variant forms of coronavirus.
Although Covid-19 gives a certain amount of immunity in a previous case, the amount of protection may change, leaving some individuals vulnerable to reinfection.
According to Deepta Bhattacharya, a professor of immunology at the University of Arizona, an antibody level is really variable after recovery from infection, and those on the lower part of the spectrum could be more susceptible to reinfection.
Researchers at the Rockefeller University, New York, examined how different types of immunity protect themselves against possible variants in a study posted on the preprint server BioRxiv. (Not peer-reviewed studies on preprint servers.)
They have designed a modified coronavirus spike protein version with 20 naturally occurring mutations to test the effectiveness of anti coronavirus antibodies.
These altered spike proteins have been tested for antibodies in lab dishes of individuals who have recovered from Covid-19, vaccinated persons, and hybrid immunity. Spike proteins have been able to escape the two first group antibodies but not hybrid immunity antibodies.
In a second study, the risk of reinfection was reduced more than doubled by researchers at the Centers for Disease Control and Prevention who had previously been infected, as opposed to natural infections alone.
Crotty says that the immunological advantage is partly due to what is called memory B cells, immune cells which shake off antibodies that combat the virus. The immune advantage of hybrid immunity.
“Memory B cells are essentially the lights that switch off anticorps plants,” said Crotty. “It’s possible for memory B cells to activate and make more antibodies when the virus passes over your first line of defense, which is circulating antibodies.
These cells are trained, after they have been exposed to a threat, to produce anticorps for specific threats [like coronavirus]. But memory B cells are not just anticorps that work in previous infections; they constantly tinker with the formula to produce anticorps that can target virus variants that may not exist yet.
The memory B cells are able to generate antibodies in both the vaccine-induced immunity and natural infection. However, research has found that the B memory cell levels in persons with hybrid immunity are on average higher than those with natural infections or vaccination alone.
In people with hybrid immunity, this could contribute to a broader range of antibodies. This recognition may go beyond the variants of the Covid-19 virus: According to a study published in June by Science journal, antibodies from hybrid immunity can also identify the original 2003 SARS virus.
The results hope Crotty that a coronavirus vaccine is possible in the future.
“You could really have a vaccine that could recognize a number of coronaviruses that are current and future, and not simply a daydream,” he said. “It’s really possible to support data.”