Is it still useful to be vaccinated after being infected with the new crown?

Achieving herd immunity by accelerating vaccination is currently a key strategy for the prevention and control of the global new crown epidemic.

Recently, "The Lancet" published two newsletters, respectively reporting the effects of two groups of formerly infected patients with a dose of BNT162b2 vaccine (jointly developed by Pfizer/BioNTech), including antibody response (humoral immunity) and T cell response (cellular immunity).

The two studies were jointly completed by scholars from Uniersity College London, Imperial College London, Public Health England and other institutions.

The researchers said that these findings have increased our understanding of the immunology of the new crown, and may also provide information for future vaccination strategies, such as performing serological antibody testing during the first vaccination, so as to allow more "second doses.

Study 1: The antibody level is more than 140 times higher after a shot of a previously infected person

The first antibody study data comes from an ongoing observational study "COVIDsortium", which included 51 medical staff in London, of which about half (24 people) had been confirmed to have been infected with the new crown virus through multiple tests.

Among medical staff who have not been infected with the new coronavirus, the peak level of antibodies against the new coronavirus S protein after vaccination is similar to the antibody level of unvaccinated patients with new coronavirus infection.

And those medical staff who have been infected in the past have significantly higher levels of antibodies against S protein after vaccination, which is on average more than 140 times the highest level of antibodies after their infection and before vaccination.

One of the research leaders, Professor Mahdad Noursadeghi, University College London, pointed out that “the infection of these medical staff first occurred in the early stages of the epidemic in London, and another dose of vaccine was administered nearly a year later, which induced a significant immune-enhancing effect, which highlighted The duration of the immune memory of the new crown infection has also strengthened our confidence.

Study 2: A shot of a previously infected person, the antibody effectively neutralizes the live virus

The second study was conducted among 72 medical staff at Imperial College London, including 21 (29%) previously infected and 51 uninfected people.

The results of immune response analysis showed that the anti-S protein antibody titer in previously infected people was significantly higher than that in uninfected people (median 16353 arbitrary unit [arbitrary unit, AU]/mL vs 615.

After vaccination, the anti-S protein antibody titer of uninfected people was negatively correlated with age, and the serological response of people over 50 years old was significantly lower than that of people under 50 years old (median 230.

Next, the researchers tested the neutralizing effect of these medical staff's serum samples on the new coronavirus, including 4 pairs of sera on the day of vaccination (4 from previously infected persons, 4 from uninfected persons) and 15 post-vaccination samples (3 Copies were from previously infected persons and 12 copies were from uninfected persons).

The results showed that for previously infected persons, regardless of the previous antibody level, vaccination induced much higher neutralizing antibody titers.

The evaluation of the T cell response also found that for the five peptides of the new coronavirus S protein, previously infected people showed a strong T cell response.

The researchers pointed out that although these immunological data are not enough to explain the clinical protection effect, it suggests that the best way to determine the vaccine supply needs to consider the immune response: on the one hand, a dose of the BNT162b2 vaccine in the previous infection will produce a stronger Humoral immunity and cellular immunity; on the other hand, the elderly or uninfected people who do not receive the second dose of vaccine in time may not provide adequate immune protection.

With the development of more vaccine research, we look forward to more evidence to guide the vaccination of a wider population, so as to optimize vaccination strategies and alleviate the development of the global epidemic as soon as possible.