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Should people who have not been vaccinated against Corona get vaccinated after being confirmed as COVID-positive? Even after 1 year and 6 months following infection, one vaccination is sufficient

Hit : 457 Date : 2022-12-19

- Vaccination 6 months after corona confirmation and Vaccination 18 months after confirmation -> similar effects

- For those who have not yet been vaccinated against the Coronavirus, one dose of mRNA vaccination is enough to form immunity

As the obligation to wear an outdoor mask was lifted from the 2nd of May, interest in the risk of infection among unvaccinated people has increased. Should unvaccinated people who have been diagnosed with Corona get vaccinated? A recent study found that a single dose of mRNA vaccine was sufficient to elicit a broad immune response 18 months after people were confirmed as positive for coronavirus. 

On the 6th, a team led by Professors Park Wan Beom, Choe Pyoeng Gyun, and Kang Chang Kyung from the Department of Infectious Diseases at Seoul National University Hospital and Professor Lee Chang-Han from Seoul National University Medical School announced the results of analyzing the immune response of a total of 43 patients who were vaccinated with mRNA vaccine 6 months or 18 months after the confirmation of the coronavirus.

In several studies, a single dose of mRNA vaccine has been reported to result in a broad immune response in COVID-19 patients. However, so far, there have been no studies on patients confirmed as having been infected with COVID who were vaccinated more than a year after infection with the coronavirus. So it is not known how long a single dose can provide a broad immune response.

According to the timing and frequency of mRNA vaccination of those confirmed as having had coronavirus, the research team studied : ▲  a unvaccinated group who had never been positive with coronavirus ▲ a vaccinated group who had never been positive with coronavirus ▲ a group which received 2 doses of vaccine and had never been positive with coronavirus ▲ a group who received 1 dose of vaccine 6 months after COVID-positive Blood samples were collected from them  ▲ a group who received 1 dose of vaccine 18 months after COVID diagnosis ▲ a group who received 2 doses of vaccine 6 months after COVID diagnosis ▲ a group who received 2 doses of vaccine 18 months after COVID diagnosis, and compared and analyzed them for changes in immune response.  

The research team evaluated the antibody titer and cell-mediated immune response to several mutant variants including Omicron.

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[Figure] Humoral responses against different strains of SARS-CoV-2 according to vaccination timing and doses after COVID-19. 

The results of the groups vaccinated 6 or 18 months after the diagnosis were similar, and increase in antibody titer after the second infections was not evident.

As a result, it was confirmed that even if the vaccine was administered 18 months after the subjects were confirmed as corona-positive, a high antibody immune response was formed at a level similar as with those to who were vaccinated after just 6 months.

In addition, even when a single vaccination was administered 18 months after a positive diagnosis, a wide range of antibody immune responses to various mutants including Omicron was observed.

In particular, as well as the antibody response to neutralize the virus, the cell-mediated immune response involved in removing the virus from the infected cells was also found to be strong.

On the other hand, the second booster vaccination did not significantly increase the immune response. This result suggests that even if the vaccine is administered twice, improvement of immune response is not evident, suggesting that one dose of mRNA vaccine is sufficient for those who have been infected with COVID-19, the research team explained.

Professor Park Wan Beom said, “There are still many unvaccinated people who have not been vaccinated due to various reasons, such as concerns about side effects after being infected with the coronavirus. It is recommended that people get vaccinated regardless of when they were infected with coronavirus.”  

The results of this study were published in the latest online edition of 'BMC Medicine', a renowned international academic journal.

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[Pictures from left] Prof Park Wan Beom, Prof Choe Pyoeng Gyun and Prof Kang Chang Kyung from SNUH Department of Infectious Diseases, Prof Lee Chang Han from SNU Medical school, Department of Pharmacology. 

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