Institute for Basic Science, Analysis Results of Antibodies in COVID-19 Vaccinated and Unvaccinated Infected Individuals
[Asia Economy Reporter Kim Bong-su] Domestic researchers have presented study results that address questions about how long antibodies formed through COVID-19 infection or vaccination maintain immune effectiveness and which variants they are effective against. It was confirmed that although different types of antibodies are formed for each variant and may be ineffective, individuals who received a third vaccine dose and then experienced breakthrough infection with the Omicron variant broadly produce antibodies capable of resisting almost all variants.
The Center for Emerging Virus Research at the Korea Basic Science Institute (IBS) announced on the 19th that it analyzed and compared the blood of unvaccinated COVID-19 infected individuals and breakthrough infection cases after vaccination to elucidate their neutralizing antibody production, immune effectiveness, and memory T cell responses.
As the dominance of coronavirus variants continues worldwide, breakthrough infections caused by new variants such as Omicron have been occurring even after COVID-19 vaccination. However, questions remained as to whether breakthrough infections were due to a decrease in neutralizing antibodies formed by existing vaccines or because there was no protective effect against new variants.
There was also no known correlation between the duration of vaccine efficacy and the number of COVID-19 vaccine doses administered, nor were there specific studies on the cross-immunity effects of currently used vaccines (developed against the original Wuhan strain) against recently emerging variants.
The research team compared neutralizing antibodies in the serum of unvaccinated patients who recovered after infection with the original COVID-19 strain, the D614G variant, or the Omicron variant, with those of patients who experienced breakthrough infection with Omicron after receiving two or three doses of the COVID-19 vaccine. For vaccinated individuals, serum samples were sequentially analyzed at 1, 3, and 5 months post-vaccination to track the duration of vaccine effectiveness and characteristics of neutralizing antibodies.
The study revealed that various coronavirus variants induce different immunogenicities. Specifically, neutralizing antibodies generated in unvaccinated individuals infected with the early circulating virus strains (Wuhan strain and related L and V variants) could not prevent infection by the Omicron variant. Conversely, neutralizing antibodies formed in individuals infected with the Omicron variant could not prevent infection by any other known coronavirus variants to date.
The effectiveness of neutralizing antibodies according to the number of vaccine doses showed that antibodies lasted longer in individuals who received three doses compared to those who received two. Neutralizing antibodies produced after two doses of the COVID-19 vaccine disappeared within five months, whereas those generated after three doses persisted for more than five months. Additionally, individuals vaccinated three times demonstrated protective effects against a wider range of coronavirus variants.
Interestingly, vaccinated individuals who experienced breakthrough infection with Omicron were found to broadly produce neutralizing antibodies capable of countering almost all reported coronavirus variants, including Omicron subvariants BA.1, BA.2, and BA.5. In this case, neutralizing antibody responses were stronger in those who had received three vaccine doses compared to two. After three vaccine doses followed by Omicron breakthrough infection, memory T cells exhibited strong antiviral responses not only to the Omicron variant but also to the original Wuhan strain at similar levels.
Choi Young-ki, head of the Center for Emerging Virus Research at IBS’s Korea Basic Science Institute, stated, “This study is significant in that it analyzed actual cross-immune responses to recent variants as well as the original COVID-19 strain,” adding, “It suggests that booster vaccinations of three or more doses can induce neutralizing antibodies against new coronavirus variants that may emerge in the future.”
Shin Eui-chul, head of the Virus Immunity Research Center at the same institute, said, “We confirmed that Omicron breakthrough infection after three vaccine doses strongly enhances memory T cell antiviral responses against both the original Wuhan virus and new variants,” and added, “Due to memory T cell responses, symptoms may be mild even if reinfected with other variants after recovering from Omicron breakthrough infection.”
This study was published in the October issue of the international journal Cell Reports Medicine (IF 16.988).
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