This is our series on key coronavirus-related information. Click here to read other installments: #Coronavirus the facts. Find the latest information and answers from experts on everything COVID-19.
Study into so-called "breakthrough" infections
Japan’s National Institute of Infectious Diseases (NIID) reports that 67 people were infected with the coronavirus during the second quarter of this year despite being fully vaccinated.
The figure was announced on July 21. It comes from information provided by municipal governments and medical institutions across Japan.
Acquiring immunity against the virus is believed to take about 14 days after receiving the recommended doses of a vaccine. Infections after that are known as "breakthrough" cases. They have been reported across Japan and other countries.
Out of the 67 cases, almost 80 percent were people in their 20s and 40s. None developed serious symptoms.
The researchers say the infections do not mean the vaccines are ineffective: "This result does not challenge the high efficacy of coronavirus vaccines. But it shows that it is still important for people to continue with anti-infection measures even after vaccination."
Misinformation on social media
After it announced the study, the NIID issued a rare statement on August 2 to counter misinformation on social media and elsewhere, suggesting its report found the vaccines did not work. It expressed "deep concern" that the findings were being distorted, adding that discussions about the vaccines should be based on science.
Vaccines are highly effective
NIID head Wakita Takaji says: "It is clear that the vaccines are effective in preventing symptoms and severe illness. Some breakthrough cases could emerge as vaccinations progress.
"However, it’s important to understand that many people are already protected from infection thanks to the vaccinations. We want to communicate with people based on science."
This information is accurate as of September 21, 2021.