The two main COVID-19 vaccines used in the US may not prevent the rare “breakthrough infection” – but even in those cases, they reduce the severity of the disease, according to a landmark study by researchers at the University of Arizona Health Services.
The Moderna and Pfizer vaccines offered more than 90% protection against infection in a study of 4,000 people – mostly Arizona medical workers and first responders.
In addition, the vaccine has halved the course of the disease and reduced severe symptoms by 58%, the researchers conclude.
The study followed a recent “superspreader” event at a White Mountain Community Dance Hall in which 22 out of 70 people became infected with COVID-19, including nine people who were reported to be partially or fully vaccinated. Navajo County and state health officials have not confirmed the infections but have started a contact follow-up based on media reports of the incident. Several of the people were hospitalized and one reportedly died.
The latest study from Arizona supports other research showing the vaccines prevent infection and serious illness. This is vital given the rapid spread of the Arizona variant of the Delta, which has devastated India. Other studies suggest that the Pfizer, Moderna, AstraZenica, and Johnson and Johnson vaccines are still effective against the Delta variant, especially when it comes to preventing hospital stays and deaths.
The UA Health Sciences study tracked 156 unvaccinated, 11 partially vaccinated, and five fully vaccinated people who developed infection, according to the study published in the New England Journal of Medicine.
Dr. Research Associate Jeff Burgess said, “If you get vaccinated, about 90% of the time you won’t get COVID-19. Even if you get it, there will be less virus in you and your disease will likely be much milder. “
The vaccines messenger RNA Moderna and Pfizer present the immune system with the spike protein that the virus uses to infect cells. This triggers an immune system response that prepares the body’s defenses for an encounter with the actual virus.
Even a dose of the two-shot vaccine reduced viral load by 40% compared to people who were not vaccinated. Viral load plays a key role in the severity of the disease.
The virus was only detectable for a week in vaccinated people who became infected. In unvaccinated individuals, the virus remained circulating in the system for two weeks or more. The risk of developing fever or other serous systems among the vaccinated fell by 58%.
The study found that a single dose of the vaccine provided 81% protection against infection and the second dose increased protection to 91%.
The university researchers relied on $ 7 million in federal funding for their ongoing AZ HEROES study and have just received a second year of funding.
“We see the same high level of effectiveness of the vaccine, so we feel good,” said Dr. Burgess. “But more importantly, we have added a number of measures of the severity of infection in people who have been vaccinated to compare with those who have not, and we have measured how much of the virus is present and how Long.”
Research team member Karen Lutrick said, “We really appreciate the participation of all of our AZ HEROES and RECOVER attendees, because without them and their work we would not have shared this information.”
To learn more about the study and the ongoing effort to recruit participants, visit azheroes.arizona.edu.
The study underscores the power of vaccines, just as a delay in the state’s vaccination campaign and the rapid spread of the new, more dangerous Delta variant have alarmed health officials.
The delta variant now makes up a quarter of the cases in the USA and is spreading rapidly in Arizona. The Delta variant first identified in India is likely twice as infectious as the original strain identified in Wuhan China. Some evidence suggests that it causes more serious illnesses as well and can infect children more easily. A recently identified “Delta Plus” strain may also prove more resistant to front-line treatments such as the use of monoclonal antibodies.
A study in the medical journal Lancet found that the hospitalization rate of people infected with the Delta strain was 85% higher than other strains.
Fortunately, the current vaccines against the Delta strain appear to be highly effective. According to a preprint study by Public Health England, two doses of the Pfizer vaccine were found to be 96% effective in preventing hospital stays in people infected with the Delta strain. Even a single dose of the Pfizer vaccine was 92% effective in preventing hospital stays.
The Moderna vaccine is expected to have a similar effect and the AstraZenica and Johnson and Johnson vaccines only slightly less.
The studies suggest that the delta variant is more likely to lead to a “breakthrough infection” in the vaccinated, even if it does not lead to hospitalization.
As a result, health officials have redoubled their appeal to people to get vaccinated.
In Arizona, cases have been rising for weeks, including a 14% increase in daily average over the past two weeks. The state reports around 500 new cases every day – with a per capita infection rate that is around twice as high as the national average.
Nationally, 47% of US citizens are fully vaccinated, compared with approximately 43% in Arizona – which takes the state and nation a long way from the relative safety of “herd immunity.”
Navajo County remains one of the state’s hot spots despite a 10% decrease in daily cases in the past two weeks. The district has a daily average of 13 new infections per 100,000 – almost twice as many as the national average.
Apache County saw the number of new cases daily decreased by 14% daily average to 5 per 100,000 – below the national average – for the past two weeks.
On the other hand, Gila County has seen a flare-up. The number of cases has increased by 25% to 8 per 100,000 – just above the national average and twice the national average.
Approximately 48% of Navajo County’s residents, 58% of Apache County’s residents, and 45% of Gila County’s residents are fully vaccinated.
Peter Aleshire covers county government and other issues for the Independent. He is the former editor of the Payson Roundup. Reach out to him at [email protected]
Comments are closed.