COVID booster shots reduce transmission of Omicron in closed environments

In a recent paper published in the journal natural medicineUS researchers investigated the infectivity of incarcerated individuals for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron infection in prisons in high-risk environments with high levels of infection.

study: Infectivity of SARS-CoV-2 breakthrough and reinfection during Omicron wave. Image credit: p.ill.i / Shutterstock

Background

Despite high vaccination rates for coronavirus disease 2019 (COVID-19) among residents, SARS-CoV-2 is transmitted at higher rates in prisons. This is due, in part, to overcrowding, poor ventilation, and virus entry from local sources. Consequently, we explore how extensive vaccination, including booster doses and prior infection, alters the course of SARS-CoV-2 transmissibility dynamics, leading to the emergence of novel and highly infectious SARS-CoV-2 variants. There is an urgent need to understand as Omicron.

Also, data on the infectivity of breakthrough and reinfection with SARS-CoV-2 Omicron in vaccinated and previously infected individuals, especially in prisons, remain limited. In other words, research should capture the broader impact of the infection environment while accounting for interactions with previous SARS-CoV-2 infections.

About research

In the current study, researchers tested 35 prisons in California, United States (USA) between December 2021 and May 2022, a period equivalent to the first five months of the COVID-19 wave. We analyzed SARS-CoV-2 surveillance data from When the Omicron subvariant BA.1/BA.2 prevailed.

They assessed the infectivity of confirmed index cases infected with Omicron in vaccinated individuals and previously SARS-CoV-2-infected individuals who shared a closed, walled cell. did. The researchers compared these results to other unvaccinated and uninfected individuals incarcerated in participating California state prisons in the United States. In addition, we stratified the results by each inmate’s vaccination status and her history of COVID-19.

The team matched 273 unvaccinated index cases and 953 vaccinated index cases within 30 days by facility and vaccination propensity scores. In addition, we matched an average of 3.5 vaccinated index cases to all unvaccinated index cases. Overall, the balance was good across the matched index cases.

Survey results

During the 5-month study period, there were 22,334 confirmed COVID-19 cases and 31 COVID-19-related hospitalizations in a study population of 111,687 (97% male). All participating California State prisons tested a resident for COVID-19 an average of 8.1 times during the five-month study period, with an average time between tests of his 11.7 days.

All persons who have been continuously incarcerated since April 1, 2020, who have been in close contact in a shared closed room, who have tested positive for COVID-19, and who have not tested positive for COVID-19 in the previous 90 days are index cases. configured. The researcher said he identified 1,226 index cases during the study period.

The mean duration of exposure of close contacts to index cases for vaccinated and unvaccinated index cases was 2.2 days and 2.4 days, respectively. However, the mean time from first exposure to testing for close contacts was 6.2 days, regardless of whether the exposure occurred from a vaccinated or unvaccinated index case. Similarly, the mean duration of follow-up COVID-19 testing in close contacts was 10 days and 10.6 days from first exposure in unvaccinated and vaccinated index cases, respectively. Vaccination of index patients did not change the spread of secondary infections from the time of exposure. Therefore, he was equivalent 6.7 days vs. 5.7 days between the two cohorts.

In an adjusted analysis, the Poisson regression model estimated that index cases who received at least one dose of COVID-19 vaccine had, on average, a 22% lower risk of transmission than unvaccinated index cases. Each additional dose reduced the risk of infection from close contact by an average of 11%.

Based on a linear combination of regression coefficients, previous infection with SARS-CoV-2 reduced the risk of infection from a proband by 23%, and immunization and SARS-CoV-2 infection together reduced this risk. Reduced by 40%. Recent vaccinations have also led to a significant reduction in infectivity. However, researchers were unable to identify an interaction between vaccination and previous natural infection related to transmission risk. So perhaps both worked independently.

Conclusion

The reduction in infection risk associated with vaccination and previous infection was additive, and although vaccination reduced infectivity even in individuals who had acquired immunity from previous infection, both SARS-CoV -2 The risk of infection could not be ruled out. prison.

Nevertheless, this study showed that each dose of the vaccine, especially the booster, provided a further relative reduction in infectivity. Moreover, the indirect effect of COVID-19 vaccination slowed transmission of SARS-CoV-2. This, combined with its direct benefits, highlights the importance of COVID-19 vaccination.

Together, these findings have the potential to inform public health policies particularly relevant to densely clustered human settlement populations such as prisons. Given the importance of timeliness of vaccination, the study also raised the possibility of timed mass vaccinations in prisons during the COVID-19 surge to slow viral transmission.The prison population Other measures, such as reductions and improved ventilation, may also protect those incarcerated.