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An American study: A previous infection with Corona may eliminate the need for two doses of the vaccine

Researchers in the United States have shown that two doses of the vaccine may not be necessary to protect against corona virus disease, among people who have already contracted the virus previously.

The study, published on the pre-print site medRxiv * and conducted on more than 100 people, found that antibody responses to a single dose of vaccine among individuals with pre-existing immunity exceeded responses among individuals who received two doses of the vaccine.

A team from the Icahn College of Medicine at Mount Sinai in New York explained that the vaccine reaction after a single dose was more common among those who had already contracted the Coronavirus in the past.

In December 2020, the US Food and Drug Administration (FDA) authorized the emergency use of two coronavirus vaccines - the Pfizer / BNT162b2 vaccine and the mRNA-1273 vaccine from Moderna.

Results from Phase 3 trials showed that, in the case of each vaccine, two doses administered with an interval of 3 to 4 weeks prevented the development of Coronavirus symptoms among participants who had not previously had a coronavirus infection.

The team says this raises the question of whether or not individuals with pre-existing immunity should receive a second dose of the vaccine.

What did the researchers do?


Researchers evaluated antibody responses among 109 established immunosuppressed individuals who received one dose of the vaccine in 2020 and another dose 3 to 4 weeks later.

They found that individuals with pre-existing immunity rapidly developed high levels of standardized IgG antibody to the Corona virus within days of vaccination.

The team also found that the reaction from a single dose of the vaccine was more pronounced among those with pre-existing immunity, as people reported side effects similar to those reported by individuals who received two doses in the Phase 3 trials.

The most common side effects were pain, swelling and fever, which occurred with the same frequency between the two groups, however, systemic side effects such as fever, headache, and muscle or joint pain were significantly more common among those with pre-existing immunity compared to those with the vaccine without infection.

The researchers say the results indicate that a single dose of a vaccine elicits very rapid immune responses among individuals with existing immunity and generates equal or higher levels of antibody titer compared to nave individuals who received the two doses.