Thousands of people have been vaccinated in clinical trials by Pfizer, Moderna, Johnson & Johnson (J&J).

According to a CDC study based on 500,000 fully vaccinated healthcare workers, two shots of the Pfizer and Moderna vaccines can reduce the risk of severe illness related to Covid-19 by 94%.

Pedestrians not wearing masks at the pier in Santa Monica, California on May 13.

A March report from the CDC found that one dose of the Pfizer or Moderna vaccine was 80% effective in preventing asymptomatic Covid-19.

In addition, research from the Israeli vaccination campaign published in the Lancet Magazine in early May also revealed that the Pfizer vaccine helps protect against the risk of hospitalization due to severe illness by 97%, and protects against death by 96%.

The J&J vaccine also has real-world effectiveness that matches the test results.

All three vaccines have proven to be so effective that on May 13, the CDC changed its guidance, allowing fully vaccinated Americans to remove masks or not need to distance when participating in indoor activities.

When variants of nCoV began to spread widely in December 2020, some scientists worried that the Pfizer or Moderna vaccines would be less effective.

From January to March, the Israeli Ministry of Health collected data from millions of people who used the Pfizer vaccine.

New research in Qatar published in the New England Journal of Medicine found that two shots of the Pfizer vaccine reduced the risk of Covid-19 infection due to the B.1.351 variant from South Africa by 75% and by 90% for the B.1.1 variant.

Clinical trials show that the Covid-19 vaccine can cause some mild short-term side effects.

However, some people who received the J&J vaccine experienced blood clots and thrombocytopenia, which did not appear in clinical trials.