Vaccines may cut Covid transmission
In a potential breakthrough in the battle against Covid-19, a new study has found that vaccines might substantially slow the transmission of the virus. Numerous vaccines have shown that they can massively cut the number of people who experience Covid symptoms or suffer serious illness or die, reports The Washington Post. But less is known about whether these shots also stop asymptomatic infections that allow the disease to keep spreading from one person to another. For the new study— which has yet to be peer reviewed— researchers at Oxford University who helped develop the AstraZeneca vaccine collected nasal swabs every week from some trial participants. They found a 67 percent reduction in positive tests after the first dose of the AstraZeneca vaccine. If the shots only made infections milder, the researchers said, the positivity rate would not have dropped. The study also found that a single AstraZeneca dose was 76 percent effective against symptomatic infections for at least three months. And the vaccine’s efficacy increased when the full two doses were given 12 or more weeks apart rather than within six weeks, from 55 percent to 82 percent. That’s a boost for the U.K.’s policy of delaying second doses in order to get first shots in as many people as possible—a strategy some scientists say the U.S. should adopt. The AstraZeneca vaccine is not expected to be authorized in the U.S. before late March.