Journal
VACCINES
Volume 10, Issue 3, Pages -Publisher
MDPI
DOI: 10.3390/vaccines10030442
Keywords
COVID-19; Omicron variant; Delta variant; breakthrough infection; cellular immunity; infection; vaccination; humoral immunity; SARS-CoV-2
Categories
Funding
- International Society for Applied Biological Sciences
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This study suggests that individuals who have recovered from SARS-CoV-2 and have been vaccinated have higher levels of cellular immunity and antibody titers, providing long-term protection. Moreover, antibody levels show a negative correlation with the time since the last contact with the viral antigen.
Previous clinical and epidemiological studies have shown that over time antibody titers decrease, and they do not provide long-term mucosa protection against SARS-CoV-2 infection. Additionally, the increase in breakthrough infections that occur more frequently in the vaccinated than in the study participants with previous SARS-CoV-2 infection has recently become a priority public health concern. We measured the amount of interferon-gamma (Quan-T-Cell ELISA) and the level of antibodies (Anti-SARS-CoV-2 QuantiVac ELISA IgG) in the blood of the same patients simultaneously to compare cellular and humoral immunity. A total of 200 study participants (before Omicron variant appearance) were divided into four groups whose levels of cellular and humoral immunity we compared: study participants previously infected with SARS-CoV-2 (group 1); study participants vaccinated with EMA-approved vaccines (group 2); study participants previously infected with SARSCoV-2, and vaccination history (group 3); and study participants without a history of SARS-CoV-2 infection or vaccination (group 4). Our results showed that study participants who received one of the EMA-approved vaccines and who recovered from COVID-19 (group 3) had significantly higher levels of cellular immunity and antibody titers in comparison with groups 1 and 2. Additionally, we have noticed that the study participants previously infected with SARS-CoV-2 and the study participants vaccinated with EMA-approved vaccines had a long-lasting cellular immunity. Furthermore, antibody levels showed a negative correlation with time since the last contact with a viral antigen, while cellular immunity within 20 months showed as long-term protection. Moreover, out of 200 study participants, only 1 study participant who recovered from COVID-19 (0.5%) was re-infected, while a total of 6 study participants (3%) were infected with SARS-CoV-2 after receiving the vaccine. This study suggests that cellular immunity-unlike humoral immunity, thanks to memory T cells-represents long-term protection in individuals recovered from SARS-CoV-2 and after vaccination.
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