Some of those previously infected with “Covid-19” think that they have become protected from re-infection with the virus and do not need to be vaccinated, and others of those previously infected think that one dose of the vaccine is sufficient for them.
And a new study by Northwestern University in the United States, published on August 30, in the Scientific Reports, shows that a previous infection alone does not guarantee a high level of antibodies against the coronavirus or a strong response after only one dose of a two-dose vaccine. .
The new study included 27 vaccinated adults in the Chicago area, some of whom had previously tested positive for the virus, and provided blood samples two to three weeks after their first and second doses of the “Pfizer” or “Moderna” vaccine, and two months after the second dose. The researchers analyzed blood samples for antibodies to the coronavirus.
When the researchers tested blood samples from participants about three weeks after the second vaccine dose, the average inhibition level was 98 percent, indicating a very high level of neutralizing antibodies.
But the levels of antibodies against the emerging variants were significantly lower, ranging from 67 percent to 92 percent, and blood samples from previously infected people collected two months after the second vaccine dose also showed that antibody responses decreased by about 20 percent. .
Another finding was that participants who had multiple symptoms of “Covid-19” had a stronger immune response to the vaccines than those who had mild or no symptoms.
“Many people and many doctors assume that any previous exposure to the virus will confer immunity against infection again, and based on this logic, some people do not believe Those who have been previously exposed to the vaccination, or if they have received the vaccination, believe they only need the first dose of two doses of the Moderna or Pfizer vaccines. Our study shows that prior exposure to the virus does not guarantee a high level of antibodies, nor does it guarantee a strong antibody response to the first vaccine dose. before”.
With regard to post-vaccination protection, McDaid notes, “The story is the same for all variants, including the delta variant, where the vaccine provides good protection, but not at the same level as the original version of the virus for which the vaccine was designed.”