Faced with the Delta variant, which is more contagious, the effectiveness of messenger RNA vaccines, Pfizer and Moderna, drops from 91% to 66% against new infections but remains very high against serious forms.
- Against severe forms, the efficacy of mRNA vaccines remains above 90%.
- Besides the Delta variant, the decline in immunity over time could explain the decrease in the effectiveness of mRNA vaccines against infections.
Vaccines continue to prove themselves to be the best anti-Covid weapon. A new real-life study highlights their effectiveness against the Delta variant. It was conducted in the United States on more than 4,000 people representing healthcare personnel and frontline workers in six states vaccinated mainly with Pfizer (65%) and Moderna (33%) but also the Janssen (2%) and who have been tested weekly with RT-PCR tests. This one was presented this Tuesday by the Centers for Disease Control and Prevention (CDC), US health officials.
New CDC MMWR study of health care and frontline workers shows that #COVID19 #vaccines reduce the risk of infection from multiple COVID-19 variants, including the #DeltaVariant. Get vaccinated if you haven’t already. More: https://t.co/4JlDusePo9 pic.twitter.com/ogYB8JQ2CG
— MMWR (@CDCMMWR) August 25, 2021
97% effective against severe forms
This study confirms the strong protection conferred by vaccines against severe forms of Covid-19. Faced with the Delta variant, which has become the majority, it remains above 90%, as reported by another CDC study, carried out on patients in New York. Figures that corroborate those reported by research carried out on patients in Los Angeles between May 1 and July 25. Also presented this Tuesday by American health officials, it indicates that unvaccinated people are 29.2 times more likely to be hospitalized with Covid-19 than vaccinated people, an efficiency of 97%.
Against new infections, the efficacy of the Pfizer and Moderna vaccines remains high but decreases due to the high contagiousness of the Delta variant. According to the new CDC study, it fell from 91% to 66%. This first figure refers to the initial study period from December 14, 2020 to April 10, 2021, so before the Delta variant became the majority. The second is the one that goes from this last date to August 14th.
The effectiveness of vaccines against infections decreases over time
The authors of the report note several caveats when releasing their findings. First, protection from vaccines might decline over time. Then, the estimate of 66% is based on a relatively short study period with few infections and needs to be confirmed.
These results underline and confirm the effectiveness of vaccines against the virus. “Although these interim results suggest a moderate reduction in the effectiveness of Covid-19 vaccines in preventing infection, the sustained two-thirds reduction in risk of infection underscores the importance and continued benefits of vaccination against COVID-19. Covid-19”, wrote the researchers.
.
