Unvaccinated COVID-19 Patients: Is One mRNA Vaccine Dose Enough?

Similar Effectiveness of Vaccination at 6 and 18 Months After Confirmation
No Significant Immune Increase After Two Doses

On April 25, 2022, a citizen is receiving a vaccine at Bumin Hospital in Gangseo-gu, Seoul, as the fourth COVID-19 booster vaccination for those aged 60 and over who made advance reservations began. Photo by Joint Press Corps (consent for portrait rights obtained).

[Asia Economy Reporter Chunhee Lee] Should you get vaccinated if you have recovered from COVID-19 after being unvaccinated? A study has found that even one dose of messenger RNA (mRNA) vaccine can elicit a broad immune response in individuals who have been confirmed with COVID-19.

Professors Wanbeom Park, Pyungyun Choi, and Changkyung Kang from the Department of Infectious Diseases at Seoul National University Hospital, along with Professor Changhan Lee from Seoul National University College of Medicine, announced these research findings on the 6th. This study analyzed immune responses in 43 confirmed COVID-19 patients who received mRNA vaccines either 6 months or 18 months after infection.

Previous studies have repeatedly reported that a single dose of mRNA vaccine induces a broad immune response in COVID-19 confirmed patients. However, it was unclear how long after more than a year post-infection a single vaccine dose could still provide a broad immune response.

The research team divided participants based on COVID-19 confirmation status and timing and number of mRNA vaccine doses into the following groups: ▲unconfirmed and unvaccinated ▲unconfirmed and vaccinated once ▲unconfirmed and vaccinated twice ▲confirmed and vaccinated once 6 months after infection ▲confirmed and vaccinated once 18 months after infection ▲confirmed and vaccinated twice 6 months after infection ▲confirmed and vaccinated twice 18 months after infection. Blood samples were collected to compare and analyze changes in immune responses.

Through this, the antibody titers and cell-mediated immune responses against various variants including Omicron were evaluated, and the results confirmed that even when vaccinated 18 months after COVID-19 confirmation, a high level of antibody immune response similar to that observed at 6 months post-infection was formed. In cases of a single vaccination 18 months after confirmation, broad antibody immune responses against various variants including Omicron were observed, and notably, not only neutralizing antibody responses but also cell-mediated immune responses involved in eliminating viruses within infected cells were measured at high levels.

Two doses did not significantly increase the immune response. The research team explained, "Even with two doses of vaccine, there was no clear improvement in immune response, suggesting that one dose of mRNA vaccine is sufficient after COVID-19 confirmation."

Professor Wanbeom Park stated, “There are still many unvaccinated individuals who have not received vaccines due to concerns about side effects after COVID-19 infection and other reasons,” and recommended, “Even if one and a half years have passed since infection, immunity against various variants can be formed with a single dose of mRNA vaccine, so vaccination should be done regardless of the time since infection.” The study results were recently published in the online edition of the international journal ‘BMC Medicine.’

This content was produced with the assistance of AI translation services.