Covid-19 survivors can develop sufficient antibodies by receiving a single dose of a Covid-19 vaccine, a Korean study showed.
According to the study, people who recovered from Covid-19 infection could enjoy a full protection effect with only one-time vaccination.
The study could back up a proposal that the health authorities change the number of Covid-19 vaccine doses for Covid-19 survivors from two to one and redirect the leftover shot to relieve the supply shortage.
Recently, Myongji Hospital’s research team, led by Professor Lim Jae-gyun at the Laboratory Medicine Department, released the study in the Journal of Korean Medical Science, with the title, “SARS-CoV-2 Antibody Response to the BNT162b2 mRNA Vaccine in Persons with Past Natural Infection.”
The study presented two healthcare workers who recovered from Covid-19 and got vaccinated with the Pfizer vaccine. The researchers observed their neutralizing antibodies and adverse reactions for a year.
The two were confirmed with Covid-19 while working in an isolated ward in April 2020. One was asymptomatic, and the other showed mild upper respiratory tract infection symptoms for 10 days but recovered.
Both of them did not have pneumonia and recovered without antiviral drugs or steroids. In addition, in blood tests two weeks and four weeks after their discharge, the researchers confirmed that they had developed immunoglobulin antibody and neutralizing antibody observed after Covid-19 infection.
The healthcare worker who recovered from a 10-day treatment in an isolated room had a 67.7 U/mL antibody titer and a 71.5 percent signal inhibition rate of neutralizing antibodies immediately after discharge. Two weeks later, the figures changed to 83.2U/mL and 56 percent, respectively.
After the first dose of the Pfizer vaccine, the antibody titer shot up to 2500U/mL, and the signal inhibition rate, 97.7 percent. However, the antibody titer remained the same after the second shot, and the signal inhibition rate slightly went down to 97.1 percent.
The other healthcare worker, who recovered after hospitalization for 17 days, had antibody titer at 1.16U/mL and signal inhibition rate at 28.2 percent immediately after discharge. Two weeks later, the figures went up to 61.6U/mL and 71.9 percent.
After getting the first jab of the Pfizer vaccine, the two figures spiked to maximum levels at 2500U/mL and 97.5 percent. After the second shot, the antibody titer was the same, and the signal inhibition rate was similar at 97.4 percent.
The two received the first dose of the Pfizer vaccine in mid-March, about 10 months after Covid-19 infection, and the second in early April.
In both cases, the researchers said the total immunoglobulin antibody was 30–40 times higher than that of antibody titer after natural infection. There was no difference in antibody titers and signal inhibition rate between the first and the second dose.
Both of them showed mild local adverse reactions in the first dose of the Covid-19 vaccine. After the second dose, they reported fever, headache, chills, and myalgia for three to four days. They had more severe adverse events after the second jab than from symptoms due to Covid-19.
Covid-19 survivors had a “booster effect,” and just a single dose can produce sufficient antibodies, Lim said.
“If the vaccination recommendation is changed to one dose from the current two doses for Covid-19 survivors, it will improve the situation concerning insufficient vaccine supply, and at the individual level, reduce adverse events due to unnecessary secondary vaccination,” he added.