Infectiousness of SARS-CoV-2 breakthrough infections and reinfections during the Omicron wave

Abstract

Breakthrough infections in vaccinated individuals and reinfections among previously infected individuals are increasingly prevalent, especially during the Omicron wave. Here, we analyze data from SARS-CoV-2 surveillance across 35 California prisons to understand the impact of vaccination and prior infection on infectiousness of individuals with SARS-CoV-2 Omicron infections in prison settings. We estimate that vaccination, prior infection, and both vaccination and prior infection reduced an index case's risk of transmitting to close contacts by 24% (9-37%), 21% (4-36%) and 41% (23-54%), respectively. Booster vaccine doses and more recent vaccination further reduced infectiousness. These findings suggest that although vaccinated and/or previously infected individuals remain infectious upon SARS-CoV-2 Omicron infection in this prison setting, their infectiousness is reduced compared to individuals without any history of vaccination or infection.

Human vaccines & immunotherapeutics: News August 2022

“…Vaccination reduces the risk of Omicron transmission by >20%, according to a study of breakthrough infections in US prisons. 1 A similar reduction was observed for prior infection, while the rate of transmission to close contacts was cut by >40% in subjects with both vaccination and past infection.…”

Infection-induced immunity is associated with protection against SARS-CoV-2 infection, but not decreased infectivity during household transmission

“…Prior transmission studies show that vaccination reduces the likelihood of transmission, [2,3] and infection-induced immunity is associated with shorter shedding duration and lower viral load; [4] however, the effect of infection-induced immunity on SARS-CoV-2 transmission has not been well established. [5] Given the high infectivity of SARS-CoV-2 and its emerging variants, many children have already been infected worldwide. [6][7][8][9].…”

The epidemiology of long COVID in US adults two years after the start of the US SARS-CoV-2 pandemic

“…5,[10][11][12][13] However, beyond female sex and presence of chronic conditions, data on risk factors vary, likely due to differences in a) study design, often lacking COVID-free or other control/comparison groups, b) population, often conducted among hospitalized or healthcare seeking populations, and/or c) case definition of long COVID. [10][11][12]14,15 Given that SARS-CoV-2 vaccines, especially without boosters, are increasingly less effective at providing sterilizing immunity against omicron variants [16][17][18][19][20] and that half of the population is estimated to have had COVID at least once 4 , understanding the prevalence of long COVID by vaccination status is critical. Limited data suggest a modest reduction in long COVID risk among vaccinated compared with unvaccinated or COVID-naive people and among unvaccinated people who went on to receive a vaccination versus people who did not.…”