This explainer is more than 90 days old. Some of the information might be out of date or no longer relevant. Browse our homepage for up to date content or request information about a specific topic from our team of scientists.
This article has been translated from its original language. Please reach out if you have any feedback on the translation.
SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics. Reporters can use these responses in news stories, with attribution to the expert.
SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics. Reporters can use these responses in news stories, with attribution to the expert.
The combination of vaccination and masking—especially in crowded or indoor areas with higher COVID-19 transmission—likely provides the best defense from breakthrough infections. In addition, if you receive the Pfizer or Moderna mRNA vaccine, make sure you get both doses and between doses, mask up. With only the first dose of mRNA vaccines, efficacy against the Delta variant is much lower than against previous variants, and you really need that second dose to reach the levels of immunity that will provide you with sustained protection.
In areas of high community transmission, vaccinated people should mask indoors to protect themselves from even mild breakthrough infections (substantial or high transmission as defined by the CDC table.)