A number of countries that vaccinated their high-risk populations with Sinovac are seeing an increase in breakthrough infections. Countries are responsible to their populations and for responding to their individual epidemiological situations. Post- introduction effectiveness studies (e.g. <https://www.nejm.org/doi/full/10.1056/NEJMoa2107715>) indicate the Sinovac vaccine has continued to perform well in preventing severe disease and hospitalization, as shown in the vaccine trials. Ongoing evidence collection from post-implementation studies to monitor vaccine effectiveness over time and against variants of concern is important and will inform the eventual need of booster doses.
- WHO does not at this time recommend a booster dose for healthy adults with any WHO-approved vaccine.