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Risk of previous SARS-CoV-2 infection and breakthrough infection after mRNA vaccination




“Are people vaccinated after SARS-CoV-2 infection better protected from breakthrough infections than people vaccinated without prior infection?”

With this question in mind, a team of Qatar researchers have found BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) vaccines from December 21, 2020 to September 19, 2021.

Recently published studies Journal of American Medical AssociationPrevious SARS-CoV-2 infections have been associated with a statistically significant reduction in the risk of breakthrough infections in both BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccine recipients. Was estimated.

Study: Relationship between risk of breakthrough infection after mRNA vaccination in Qatar and previous SARS-CoV-2 infection. Image credit: NIAID

SARS-CoV-2 infection and immune status in Qatar

The coronavirus disease 19 (COVID-19) vaccination drive began in December 2020 in Qatar, initially with the BNT162b2 (Pfizer-BioNTech) vaccine, and three months later with the addition of the mRNA-1273 (Moderna) vaccine. .. Then, from January to June 2021, the country experienced two SARS-CoV-2 waves, with alpha (B.1.1.7) and beta (B.1.351) variants predominant.

By the summer of 2021, Delta had become the predominant variant. Throughout the scenario, the team has the opportunity to assess whether those vaccinated with a previous SARS-CoV-2 infection have a lower incidence of breakthrough infections than those vaccinated without a previous infection. I got it.

Study design

The association between previous infections and the acquisition of infections after vaccination was investigated using two retrospectively matched cohort studies. The study utilized a national federated database that collected all data related to SARS-CoV-2, including infections since the onset of the epidemic, immunization, and details of relevant individual demographics. The eligible research population included a total of 1,531,736 eligible BNT162b2 and mRNA-1273 vaccinated individuals in the Federated Database between December 21, 2020 and September 19, 2021. ..

Documented incidence of SARS-CoV-2 infection after the second vaccination, a cohort of individuals who experienced a PCR-confirmed infection prior to vaccination, and a record of previous infections in both vaccine cohorts. Compared with the incidence of those who do not have. Follow-up continued from 14 days after the second dose to the earliest occurrence of any PCR positive. Nasopharyngeal swab, Cause of death, or censorship at the end of the study (September 19, 2021).

Individuals based on previous infection status at a ratio of 1: 1 per calendar week of gender, age group of 5 years, nationality, and first vaccination to control the difference between exposure risk and mutant exposure I matched it accurately. The cumulative incidence of infection was calculated using the Kaplan-Meier estimation method.

An additional analysis was performed to assess the association between the timing of vaccination-enhancement of innate immunity and the incidence of breakthrough infections.

Investigation result

The BNT162b2 vaccination cohort consisted of 99,226 previously infected individuals (PCR-positive nasopharyngeal swabs) and 290,432 previously uninfected matched individuals. Of these, 159 reinfections and 2509 reinfections occurred 14 days or more after the second dose.

Cumulative infection rates for BNT162b2 vaccinated individuals were 0.15% (95% CI, 0.12% -0.18%) for those who were pre-infected in 120 days and 0.83% (95% CI, 95% CI, for those who were not. It was estimated to be 0.79% -0.87%). follow up.Cumulative infection rates appeared to accelerate among those who were not pre-infected after 110 yearsNS Follow-up day.

For mRNA-1273 vaccination, 58,096 uninfected individuals previously confirmed by PCR and 169,514 matched individuals made up the cohort. Vaccinated individuals, with or without pre-infection, had 43 and 368 reinfections, respectively. It has an estimated 0.11% (95% CI, 0.08% -0.15%) cumulative infection rate in people infected after 120 days and 0.35% (95% CI, 0.32% -0.40%) in previously uninfected people. Was interpreted as. -Up. Here, in individuals vaccinated with mRNA-1273, the cumulative incidence of infection appeared to accelerate among individuals vaccinated who had not been pre-infected since 1980.NS Follow-up day.

In this study, people who were vaccinated with SARS-CoV-2 more than 6 months before the first dose were at greater risk of breakthrough infection than those who were infected within 6 months of the first dose. Was found to be significantly lower.


Given the use of large datasets, this study establishes credibility for impacts on a wider population around the world.

“Previous infections in vaccinated individuals (a hybrid of innate and vaccine immunity) appeared to be associated with a further reduction in breakthrough infections,” the team concludes.

The incidence of breakthrough infections increases over time after the second dose among previously uninfected individuals, suggesting that vaccine-induced immunity declines over time.

Evidence suggests that the mRNA-1273 vaccine protects better than BNT162b2. Nonetheless, the team found that the difference in the incidence of breakthrough infections observed in vaccinated individuals was an additional week interval between two doses of mRNA-1273 (longer dose intervals). May be associated with improved immunity) and speculate that it may be due to larger doses of mRNA-1273.





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