The effectiveness of the three COVID-19 vaccines available in the United States has declined in recent months, with protection against infection falling under 50 percent for two of them after six months, according to a new study.
Moderna’s COVID-19 vaccine dropped from 89.2 percent in March to 58 percent in September, researchers found. During the same period of time, Pfizer’s COVID-19 vaccine dropped from 86.9 percent effective to 43.3 percent, and Johnson & Johnson’s shot dropped from 86.4 percent to 13.1 percent.
Dr. Stephen Hahn, the head of the Food and Drug Administration during the final portion of the Trump administration, said last year that the agency wouldn’t authorize COVID-19 vaccines that weren’t at least 50 percent effective against infection.
Researchers also found that the vaccines’ protection against death waned after six months, particularly among older people. Instead of comparing the effectiveness in March and September, though, they used the data to pinpoint the effectiveness from July to October. For those 65 or older, the effectiveness against death was 75.5 percent for Moderna’s vaccine, 70.1 percent effective for Pfizer’s vaccine, and 52.2 percent effective for Johnson & Johnson’s jab.
For younger people, the effectiveness was higher: 84.3 percent for Pfizer’s, 81.5 percent for Moderna’s, and 73 percent for Johnson & Johnson’s.
While early data showed high vaccine effectiveness against both infection and death, “our results suggest vaccines are less effective in preventing infection associated with the Delta variant,” researchers wrote.
While the vaccinated as time wore on faced a higher risk of getting infected with COVID-19 or dying, the unvaccinated were still more likely to contract the illness or die from it, they added.
Researchers with the Public Health Institute, the University of Texas School of Public Health, and the Veterans Affairs Medical Center carried out the research, which was published in the journal Science.
