The COVID-19 vaccine largely defends against the highly contagious variant of the delta coronavirus, especially when it comes to preventing severity and death. These are the results of three studies published by the Centers for Disease Control and Prevention (CDC).
According to the study, fully vaccinated people were 5 times less likely to be infected with delta, 10 times less likely to be hospitalized with the delta version of COVID-19, and 11 times less likely to die from the variant.
Reporting from Arstechnica, Saturday (11/9/2021) The emergence of the delta version of COVID-19 has raised concerns that the effectiveness of the vaccine will decrease, but data shows that the injection is holding up quite well. The effectiveness of existing vaccines against infection has decreased some with the dominance of the delta variant, but vaccination still offers strong protection, both from hospitalization and from death.
In one of three studies, public health researchers looked at data from more than 600,000 adult COVID-19 cases in 13 US jurisdictions over two time periods: the pre-delta period from April 4 to June 19, and the post-delta period from June 20 to June 19. July 17th. The investigators then calculated standardized ratios of case age, hospitalization, and death between fully vaccinated and unvaccinated in each of the two periods.
In terms of infection, fully vaccinated persons were about 11 times less likely to develop infection in the pre-delta period, compared with unvaccinated (with a 95 percent confidence interval from 7.8 to 15.8). That ratio drops to 4.6 less likely in the post-delta period (with a 95 percent confidence interval from 2.5 to 8.5).
For pre-delta hospitalizations, fully vaccinated persons were 13 times less likely to end up in hospital than unvaccinated (11.3 to 15.6) confidence intervals. After delta, the ratio drops slightly to 10 times less likely (8.1 to 13.3 confidence intervals).
Fully vaccinated people were 16.6 times less likely to die from COVID-19 before the delta (13.5 to 20.4) and 11.3 times less likely to die after the delta (9.1 to 20.4 confidence interval) 13,9).
These findings are "consistent with the potential for decreased vaccine protection against confirmed SARS-CoV-2 infection and continued strong protection against hospitalization and COVID-19-related death," conclude the study authors.
When they further refined the data to account for vaccine coverage over two time periods, the researchers calculated a rough estimate of how vaccine effectiveness changed over the two intervals. For the vaccine's protection against infection, they estimated the effectiveness to drop from 91 percent to 78 percent with delta. For protection against hospitalization, effectiveness appeared to increase from 92 percent to 90 percent, and for mortality, from 94 percent to 91 percent.
One troubling note is that the decline in protection was more pronounced in the older age group, with those aged 65 and over experiencing the greater decline.
The findings are in the second study, which looked at nearly 33,000 cases of COVID-19 a from hospitals, emergency departments and emergency care clinics. The researchers split the data by age; the vaccine's effectiveness against hospitalization was 89 percent among people aged 18 to 74, but only 76 percent among people 75 years and over.
In a third, smaller study involving more than 1,000 people at five Veterans Affairs Medical Centers, researchers again saw a decrease in the vaccine's effectiveness by age against hospitalization. Overall, the vaccine was 87 percent effective at preventing hospitalization in the middle of a delta attack. When divided by age, the vaccine is 95 percent effective in people 18 to 64 years old, but only 80 percent for those 65 years and over.
