A single dose of Covishield vaccine can lower the risk of viral transmission within a household by almost 50%. In the study published in Public Health England, it was shown that people who became infected with COVID 19 three weeks after getting a single dose of these vaccines were between 38 percent and 49 percent  less likely to spread the virus to someone in their household compared to those who were vaccinated. 

Following 14 days post-vaccination, protection was initiated and similar levels of protection were observed in people irrespective of their age. The study suggested that households are high-risk settings for virus transmission, and similar results could be anticipated in different settings with similar transmission risks, such as prisons, hostels. 

This protection is over the reduced risk of a vaccinated individual developing symptomatic infection; around 60-65%-4 weeks after one dose of either vaccine. The above study included more than 57000 contacts from 24000 households with a confirmed case of COVID 19 in someone who had received a vaccine. It was compared to nearly 1 million contacts of unvaccinated cases. 

The study reinforced that vaccines are crucial in helping us return to a normal life. Vaccines will help in reducing the severity of illness and prevent hundreds of deaths daily, they have an additional effect on lowering the probability of transmitting COVID 19 to others. 

Source:

1. https://www.gov.uk/government/news/one-dose-of-covid-19-vaccine-can-cut-household-transmission-by-up-to-half
2. https://www.beckershospitalreview.com/pharmacy/single-vaccine-dose-can-reduce-covid-19-transmission-by-half-uk-study-finds.html