The effect of previous COVID-19 infection on the efficacy of vaccines against SARS-CoV-2 has not been fully elucidated.
The Doctors of the Therapeutic Clinic of the Medical School of the National and Kapodistrian University of Athens Theodora Psaltopoulou, Giannis Danasis, Panos Malandrakis and Thanos Dimopoulos (Rector of EKPA) summarize the results of the relevant publication of LJ Abu-Raddad and associates in the prestigious scientific review JAMA 2021; 326 (19): 1930-1939.
The aim of the study was to evaluate the protection against COVID-19 after vaccination with mRNA vaccines against SARS-CoV-2 in individuals who had previously had COVID-19 disease compared with those who had no previous history of COVID-19.
The study was conducted in Qatar and included a total of 1,531,737 people who had been vaccinated with either BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna). Participants were vaccinated between 21 December 2020 and 19 September 2021 and follow-up started 14 days after receiving the second dose of the vaccine until 19 September 2021. All COVID-19 cases were confirmed by the polymerase chain reaction (PCR) molecular method in nasopharyngeal smears.
In the subgroup of participants receiving BNT162b2 99,226 people had a previous history of COVID-19 and 290,432 people had no previous history of COVID-19. The median age was 37 years, while 68% were men.
In the subgroup of participants who received mRNA-1273, 58,096 people had a previous COVID-19 disease and 169,514 people had a previous history of COVID-19. The median age was 36 years, while 73% were men.
Among those who received BNT162b2, 159 cases of COVID-19 were found in those with a previous history of COVID-19 and 2509 cases of COVID-19 in those who had not previously had SARS-CoV-2.
Among those who received mRNA-1273, 43 cases of COVID-19 were found in those with a previous history of COVID-19 and 368 cases of COVID-19 in those who had not previously had SARS-CoV-2.
The cumulative incidence of COVID-19 among those vaccinated with BNT162b2 was 0.15% in subjects with a previous diagnosis of COVID-19 versus 0.83% in subjects without prior COVID-19.
The cumulative incidence of COVID-19 among mRNA-1273 vaccinated was 0.11% in those with a previous diagnosis of COVID-19 versus 0.35% in those without a previous COVID-19.
Differences in percentages between vaccines are not a comparison of efficacy between vaccines as the study was not designed for this purpose and did not have the required statistical validity.
In addition, it should be noted that those vaccinated with SARS-CoV-2 at least 6 months prior to the first dose of SARS-CoV-2 vaccine had a significantly lower risk of re-infection after vaccination than those who had been ill for less than 6 months. from the first dose of the BNT162b2 vaccine or mRNA-1273.
In conclusion, the individual history of previous COVID-19 infection was associated with a significantly lower chance of COVID-19 after vaccination with SARS-CoV-2 mRNA vaccines, while protection was stronger among those vaccinated after at least 6 months of disease.
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