A new CDC study shows that isolating in separate rooms significantly reduced the odds of SARS-CoV-2 transmission between household members. Isolating in separate rooms proved to be the most effective mitigation measure against onward SARS-CoV-2 virus transmission regardless of age, gender, vaccination status, and other risk factors.
While vaccination was found to reduce the risk of infection, it did not appear to reduce transmission within the household. Both vaccinated (primary vaccination series) and unvaccinated adults and children with varying demographic factors were found to transmit the virus at similar rates. The study serves as a reminder that we should not ignore public health and nonmedical interventions such as masking and isolating, even as mandates are dropping and much of the world is experiencing fatigue.
The study used data from 513 households with children under the age of 18 and 2,053 people. Data was collected from August 2020 to August 2021 in Utah, September 2020 to August 2021 in New York City, and November 2020 to October 2021 in Maryland. This means the study was conducted before the emergence of the Omicron variant and the availability of vaccines for most children in the United States.
To assess how SARS-CoV-2 virus was transmitted in households, study participants self-collected nasal swabs weekly and with the onset of acute illness, which were sent to a laboratory for PCR testing. The study followed participants through the Alpha and Delta waves. Consistent PCR testing allowed the researchers to capture both asymptomatic and symptomatic infections. Participants also completed weekly questionnaires about symptoms experienced in the preceding week and, if symptomatic, what preventive measures they took, such as isolating or wearing a mask.
Primary cases were defined as participants with the first symptom onset or positive SARS-CoV-2 test, whichever occurred earlier. However, as several household members were often infected at the same time, co-primary infections were excluded from the transmission analysis. The researchers found that 1 in 4 households experienced onward spread of SARS-CoV-2 among household contacts.
In addition to isolating in separate rooms, household members should also remain in isolation until they test negative on a rapid antigen test, despite the current recommendation of 5 days. A recent study found that 62% of patients were still shedding infectious viruses by day 5, and 23% were still shedding infectious virus by day 7. Those taking Paxlovid should also be aware of the possibility of a rebound infection and return to isolation if necessary.
By employing these mitigation strategies, we can ensure that we are minimizing the chances of spreading Covid-19 to our loved ones and co-habitants.