Large-scale study of Qatar’s population

Immunization against COVID-19 began in Qatar in December 2020, with Pfizer-BioNTech and then the Moderna vaccine being the most vulnerable, first distributed to front-line healthcare professionals. As of August 2021, it is estimated that more than 80% of all individuals over the age of 12 received one of the mRNA vaccines twice, but nonetheless, SARS-CoV-2 infection was in the region. It is reported to be increasing in.

Papers recently uploaded to the preprint server medRxiv* By Chemaitelly et al.. (August 27, 2021), the long-term efficacy of the mRNA vaccine will be analyzed among the Qatar population. In this study, it was observed that the defense against infection decreased about 6 months after vaccination, but the defense against death and hospitalization remained.

How was the study conducted?

Since the beginning of the COVID-19 pandemic, this group has used information from the Qatar SARS-CoV-2 database nationwide, including all PCR tests, vaccinations, and relevant demographic data for each individual. .. Vaccine efficacy was estimated by comparing infection rate, disease severity, and vaccination status. Only individuals who received the Pfizer-BioNTech vaccine twice were included in the study to eliminate variations due to heterogeneous administration.

Positive PCR tests in which an individual did not report symptoms were considered asymptomatic, vaccine efficacy was also reported for the probability of developing symptoms, age, gender, race, and SARS-CoV-2 mutations. Further analysis based on the body. Due to the average young population of Qatar, the average age of participants is 31.5 years, about 70% of whom are male, and other demographics proportionally represent the general population.

Breakthrough case

Data from approximately 200,000 people were included in the study, and the authors found that as of August 15, 2021, 8,155 people who received a single dose of the Pfizer-BioNTech vaccine were infected with SARS-CoV-2 and 8,935. States to be infected. Individuals who received both doses became infected. In the early stages of vaccine distribution, the proportion of individuals with breakthrough infections was very low, less than 5%, given the low proportion of the population still vaccinated. At the peak of the beta variant wave in the country in April 2021, breakthrough cases rose to almost 15% and then rose above 35% in an irregular manner.

Approximately three-quarters of all breakthroughs were among patients who received the Pfizer-BioNTech vaccine instead of the Moderna vaccine, but the number of people who received the former was about double, predominantly the earliest. The most vulnerable and introduced bias. Of the patients who received only one Pfizer-BioNTech vaccine, 377 were hospitalized with severe COVID-19 as of August 15, but of the more severely ill patients compared to 96 who received both. There are 31 and 8 people in similar proportions. , And among the deceased: 34 and 15.

Protection against infection and death

Like other reports, the author mentions the vaccine Effectiveness Drag resistance to infection is negligible 2 weeks after the first dose and reaches a peak of approximately 70% protection 5 weeks after the second dose. In fact, the study reported that efficacy declined slightly 0-4 weeks after the second dose, and after 15 weeks there was little change by gender, age, or race, and declined more rapidly. increase. Efficacy against symptomatic infections was observed to peak about 5 weeks after receiving the second vaccination, followed by a similar decline, followed by a more rapid and steady decline in 15-20 weeks. rice field. Protection against symptomatic infections was consistently higher than protection against asymptomatic infections, but peaked at nearly 80% compared to 63.7%.

Importantly, the reduction in efficacy for hospitalization or death was much less, not reduced until 25 weeks after the second dose. It was found that protection against hospitalization and death was stable at about 90% for 6 months after vaccination and then dropped to about 70%. These later time points reflect the most vulnerable of the first vaccinated population and can be biased by other comorbidities and increased likelihood of infection. However, the group states that the same pattern of decline in protection was observed in all age groups and is likely to represent the general public.

Protection against Variant of Concern

Qatar experienced two major SARS-CoV-2 waves in 2021. The first wave was characterized by a mixture of alpha and beta mutants of concern, the latter dominated by highly contagious delta mutants. Vaccine efficacy was also compared weekly for thousands of individuals infected with alpha, beta, or delta variants, as confirmed by genomic testing. For example, 5-9 weeks after the second dose, the vaccine provided 82.2% protection against infection from alpha mutants, 52.7% protection from beta, and 72.0% protection from delta, but protection at 15-19 weeks. The level was 11.9%. 47.7% and 13.0%, respectively.

Given the observed reduction in efficacy in tracking individuals infected with each particular strain, the potential for reduced protection from exposure to new mutant strains of concern was also rejected by the group. Qatar, Israel, and the United States have reduced the interval between vaccinations to three weeks. These countries report that protection from mRNA vaccines is significantly weaker than in the United Kingdom and Canada, which have implemented later vaccination schedules. The authors speculate that this has not yet been confirmed, but may explain the reported discrepancies observed between these locations.

The majority of the vaccinated population may be at risk of a significant reduction in vaccine-induced protection against SARS-CoV-2 infection. Early 2021. The study found long-lasting protection from hospitalization and death, but boosters may be needed to strengthen this and prevent further diminished protection.

*Important Notices

medRxiv Publish preliminary scientific reports that should not be considered definitive as they are not peer-reviewed, guide clinical practice / health-related behaviors, and should not be treated as established information.