Since the first outbreak in Wuhan 2019, the SARS-CoV-2 virus has spread worldwide, and on the different continents, new mutated variants have started to emerge. The available Covid-19 vaccines such as Pfizer BioNTech, Moderna, AstraZeneca or Johnson & Johnson protect fully vaccinated people from hospitalization and death, but their effectiveness is lower against some strains. The Delta variant, which originated in India in 2020, has become the dominant strain in the U.S due to its high transmissibility levels. According to recent reports, the Delta variant can spread easier through vaccinated people than other variants.
Vaccinated people can still pass the Delta strain to others
According to the newest studies, fully vaccinated individuals that get infected with the Delta strain are safe from severe illness, but they can spread the infection just as easy as unvaccinated individuals. This is why CD changed guidelines and recommends that everyone, regardless of vaccinations status, wear masks in public indoor places or at crowded events.
It is not clear to what extent fully vaccinated people contribute to the surge of new daily cases
Scientists from different medical fields such as epidemiologists, virologists, and other health experts are researching how vaccinated people contribute to the rising infection numbers. A study conducted by David O’Connor at the Madison and Dane County health department in Wisconsin shows that vaccinated people can spread the infection. The study compared Ct values of 719 people, and out of 112 sequenced samples, 90% of the infections were the Delta strain.
This is not the first time research shows that vaccinated people can get infected with the Delta strain. Last month in Provincetown, Massachusetts, more than 469 vaccinated people got infected after joining big crowds. The Ct levels of both vaccinated and unvaccinated people were low, meaning that both categories had high viral loads. 133 of the samples sequences were positive for the Delta strain. More research is needed to establish to what extent can fully vaccinated people infect others.