The second injection of the COVID-19 vaccine may not be necessary in previously infected individuals: a study

A single injection of one of the currently authorized COVID-19 vaccines may be sufficient to provide immunity to individuals who were previously infected with the virus, thus eliminating the need for a second dose and helping to stretch the severely limited vaccine stock, a study by O Mount Sinai found it. This change in public health policy could also save these individuals from the unnecessary side effects of a second dose of the vaccine, which the researchers found to be significantly greater in individuals with pre-existing immunity to SARS-CoV-2, the virus that causes COVID – 19 A letter to the editor was published today in New England Journal of Medicine detailing the study.

“We have shown that the antibody response to the first dose of the vaccine in people with pre-existing immunity is equal to or even exceeds the response in uninfected people after the second dose,” says co-author Viviana Simon, MD, Ph. D., Professor in the Departments of Microbiology and Medicine (Infectious Diseases) at the Icahn School of Medicine on Mount Sinai. “For this reason, we believe that a single dose of the vaccine is sufficient for people who have already been infected with SARS-CoV-2 to achieve immunity.”

Two COVID-19 vaccines (Pfizer-BioNTech and Moderna) received emergency use authorization from the United States Food and Drug Administration (FDA) in December 2020 and were administered to millions of people across the country. In Phase 3 trials, both vaccines reported high efficacy in preventing symptomatic infections by COVID-19 after two doses administered three to four weeks apart. Both vaccines are also well tolerated with few side effects that require additional medical attention.

In their study of 109 individuals with and without previous immunity against SARS-CoV-2, researchers at Mount Sinai, led by Dr. Simon and co-author Florian Krammer, Ph.D., Professor of Vaccinology in the Department of Microbiology, found that o The first group developed antibodies within a few days after the first dose of the vaccine at a rate of 10 to 20 times greater than those who were not infected, and at a rate of more than ten times after the second dose. “These findings suggest that a single dose of the vaccine elicits a very rapid immune response in individuals who test positive for COVID-19,” said Dr. Krammer. “In fact, that first dose immunologically resembles the booster dose (second) in people who have not been infected.”

The team also investigated systemic reactions after the first dose of the vaccine in a second group of 231 subjects, 83 of whom tested positive for COVID-19 and 148 did not. Although vaccines were generally well tolerated, symptoms at the injection site – including pain, swelling and redness of the skin – were found in both subgroups. In recipients with pre-existing immunity, however, side effects occurred significantly more frequently, including fatigue, headache, chills, fever and muscle or joint pain.

The intensity of the response to the first dose in people previously infected appears to be similar to the response of people not previously infected after the second dose. The reason for the stronger response in both groups is probably due to the fact that the body has already been “prepared”, which means that the immune cells have learned to recognize the virus’s spike protein – the antigen that forms the basis of vaccination. . These cells therefore respond more vigorously, leading to stronger reactions to the vaccine.

If an individual’s history of infection is unknown, Dr. Simon suggests using a serological test to detect antibodies that may exist for the peak protein. “If the screening process determines the presence of antibodies due to the previous infection, a second injection of the coronavirus vaccine may not be necessary for the individual,” he concludes. “And if this approach were to translate into public health policy, it could not only expand the limited stock of vaccines, but control the most frequent and pronounced reactions to vaccines experienced by survivors of COVID-19.”