In addition, questions about transmission remain unanswered. Vaccinated people with asymptomatic or breakthrough infections may still be able to pass the virus on to others, but it is not yet clear how often this happens.
Until that science is more definitive, or until vaccination rates go up, it’s best to stay on the safety and regular testing side, many experts said. At the Olympics, for example, frequent testing could help protect the broader Japanese population with relatively low vaccination rates, as well as potentially older and riskier support workers.
“It’s these people who I really worry about the most,” said Dr. Lisa Brosseau. a Research Advisor at the Center for Infection Disease Research and Policy at the University of Minnesota.
Not only can they become infected with the virus, which puts additional strain on the Japanese health system, but they can also become sources of transmission: “Everyone is at risk and anyone could potentially be infected,” she said.
According to the Tokyo 2020 Press Office, all Olympics staff and volunteers were given the opportunity to get vaccinated, although officials did not provide any information on how many had received the syringes.
Instead of testing less frequently, officials could rethink how they respond to positive tests, said Dr. Binney. For example, if someone who is vaccinated and tested positive asymptomatically should still be in isolation – but perhaps close contacts could simply be monitored instead of being quarantined.
“You are trying to balance the disruptive nature of what you do when someone tests positive against any benefit in slowing or stopping the spread of the virus,” said Dr. Binney.