A new household study reveals that people fully vaccinated against COVID-19 are as equally infectious as unvaccinated individuals, but for a shorter period of time.

Previous studies indicated that an individual with two doses of a COVID-19 vaccine has a lower risk of contracting the virus and will likely recover from any symptoms more quickly. This study found that vaccinated participants can still carry a viral load comparable to an unvaccinated individual at the peak of infection.

The study from the United Kingdom included 621 participants identified using the UK’s contact-tracing system between September 2020-2021. Those enrolled in the study had the Delta variant of the SARS-CoV-2 virus with mild or no symptoms. Daily testing was administered for all participants, regardless of symptoms, to determine whether infection was active.

According to the study leader, Ajit Lalvani, DM, of Imperial College London, the similarity of the viral load between vaccinated and unvaccinated individuals explains why the Delta variant is easily transmitted in close quarters, even among fully vaccinated people. The findings may also support the high case numbers emerging worldwide, even in populations with high vaccination rates.

How to Protect Groups Susceptible to Infection

Despite rising vaccination rates in the population, the Delta variant is causing an increase in case numbers. The study found that while vaccines are an effective preventative measure to avoid severe symptoms and complications from COVID, they are not sufficient to prevent the spread of the Delta variant in close quarters. Lalvani and his colleagues advise people at risk for severe illness to take additional precautions, such as wearing masks, and social distancing.

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