Study of U.S. Blood Donors Finds Nearly Half of Population Display Hybrid Immunity to COVID-19

recently Morbidity and Mortality Weekly Report (MMWR), Researchers estimated the seroprevalence of severe acute respiratory syndrome coronavirus type 2 (SARS-Co-V2) among blood donors in the United States (US) from April 2021 to September 2022. We also estimated the incidence of primary infections during the same period stratified by 2019 coronavirus infection ( COVID-19) vaccination status.

To this end, the researchers analyzed a national longitudinal cohort of 142,758 blood donors who donated blood two to three times in 2020. The Centers for Disease Control and Prevention (CDC) includes the Red Cross, Vitalent, Creative Testing Solutions, and Westat.

study: Estimated SARS-CoV-2 seroprevalence and incidence of first-onset SARS-CoV-2 infection among blood donors by novel coronavirus vaccination status — United States, April 2021–September 2022. Image credit: next143 / Shutterstock

Background

From the beginning of the COVID-19 pandemic through the end of 2022, changes in COVID-19 testing behaviors and test reporting requirements have led authorities to prevent SARS-CoV in the United States. It became impossible to estimate the primary infection burden of -2. However, this data has public health implications. For example, it could help identify population subsets at high risk of infection and devise targeted strategies to reduce risk.

About research

In this study, researchers will target CDC cohorts in the first three quarters of 2022 and the first quarter of 2021 to test for antibodies to the SARS-CoV-2 spike (S) and nucleocapsid (N) antigens. One sample per blood donor was randomly selected from They also checked whether donors had been vaccinated against COVID-19 at each blood donation visit.

Additionally, the team weighted the selected sample data into cohorts by considering two factors:

i) Response within four quarters.

ii) Demographic differences between blood donors and the general US population.

The researchers estimated vaccine immunity, induced immunity, or hybrid immunity based on each study participant’s antibody test results and COVID-19 vaccination history. In addition, we estimated the number of people whose immune status changed between the two quarters. This criterion limited this analysis to his 72,748 blood donors, or 51% of cohort strength. Therefore, the iterative weight adjustment method helped to combine stratification and raking to obtain weights.

In addition, the team estimated seroconversion from anti-N-negative to anti-N-positive individuals across all four quarters included in the study. They stratified the estimates by race/ethnicity and four age groups (16–29, 30–49, 50–64, and ≥65). This cohort consisted primarily of people of her four ethnicities, including Asians, Blacks, and Hispanics.

Finally, the team presented seroprevalence and infection rates as weighted averages and used a two-tailed t-test to compare these results. They stratified the comparative results by demographics and vaccination status, with a significance level of α equal to 0.05.

Prevalence of vaccine-induced immunity, infection-induced immunity, and hybrid* immunity^† SARS-CoV-2 vs. Age Groups in Blood Donors Age 16+—United States, April 2021–September 2022

result

In this study cohort, an estimated 96.4% of those aged 16 years and older have infection- or vaccination-induced SARS-CoV-2 antibodies, of which 47.7% will have hybrid immunity by the end of Q3 2022. was 22.6% of people acquired immunity through natural infection and 26.1% through vaccination.

N antibody seroconversion indicates natural SAR-CoV-2 infection. The study found that unvaccinated people had higher infection rates than vaccinated people, indicating that vaccination provided some protection against SARS-CoV-2 infection. I’m here. It may also be due to differences in protective behaviors such as masks and social distancing between vaccinated and unvaccinated people.

During the period when the SARS-CoV-2 omicron variant predominated, the relative difference in infection rates narrowed, presumably because vaccine protection declined rapidly over time post-vaccination. be done. Omicron also evades all induced immunity to cause breakthrough infections. However, by late 2022, the difference in infection rates between vaccinated and non-vaccinated people had also narrowed, as vaccinated and non-vaccinated people adopted largely similar preventive behaviors.

Similarly, the incidence of index SARS-CoV-2 infection was higher in young compared with older adults and lower in Asians compared with other races and ethnicities. However, these differences between all groups evaluated also decreased over time. Interestingly, the prevalence of hybrid immunity was highest among black and Hispanic people compared with Asians and whites.

Conclusion

In the report, researchers found that nearly 50% of immune-competent people over the age of 16 had hybrid immunity, and two-thirds had a natural infection. Both infection-induced immunity and hybrid immunity increased during the study period, but the prevalence of hybrid immunity remained low in adults aged 65 years and older. These results demonstrate the positive and beneficial effects of increased vaccination coverage and immediate access to COVID-19 vaccines for older adults in the United States and around the world.

In addition, older adults, i.e., those aged 65 and older, adhered to recommended behaviors to avoid SARS-CoV-2 infection more than the other three age groups monitored in this study. Nonetheless, as the results of this study suggest, for those at high risk of severe SARS-CoV-2 infection, and even those who are not, at least one dose of bivalent vaccination, including It is important to stay up-to-date on recommended COVID-19 vaccinations.