A team of researchers from Florida, U.S. studied the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission from individuals with delta breakthrough infections.
The coronavirus pandemic has brought unprecedented challenges to the healthcare sector across the globe. As the COVID-19 pandemic progressed, several new variants with higher transmissibility and pathogenicity had evolved across the globe. The World Health Organization has designated some of the variants such as delta as Variants of Concern. Delta variant was first identified in India. This variant is more infectious as it contains multiple spike mutations. Owing to this characteristic, delta variant is resistant to infection- or vaccination-induced immunity. In the current study, the researchers have studied the linkage of the delta variant with a higher rate of vaccine breakthrough infections. Moreover, they investigated if a fully vaccinated individual is able to transmit the virus to others. The researchers conducted phylogenetic analysis and contact tracing to estimate the chances of direct viral transmission between vaccinated individuals. In this context, it is to be noted that in Florida during July 2021 a sudden increase in delta-induced vaccine breakthrough cases was observed. Importantly, out of 109 infections in Florida, 58 infections were due to delta variant. The researchers observed higher frequency of delta infection in unvaccinated people in comparison to vaccinated people. They found that a large number of cases were due to community-level transmission, healthcare-related exposures, and household transmissions. The study reveal that direct viral transmission may occur between fully vaccinated people with delta infections. However, the researchers added that the viral transmission potency of delta-induced breakthrough cases varies with the vaccine type or time since full vaccination.
In a nutshell, the researchers revealed that even after full vaccination COVID-19 vaccines may not be fully effective in reducing the risk of person-to-person SARS-CoV-2 transmission. The researchers stressed on the further studies to investigate the effectiveness of a third booster dose to combat breakthrough coronavirus infections.