VA Study Sought to Determine ‘Read-World’ Effectiveness
A Montana VA nurse administered the Moderna COVID-19 vaccine to a veteran at the Montana VA Health Care System vaccination clinic this spring. or Montana veterans at the Helena Aviation Readiness Center, March 20, 2021. Eighteen Army National Guard photo by Spc. Emily Simonson
PITTSBURGH — Veterans enrolled in VA care are not a typical population of U.S. patients. Because of older age, higher burden of comorbidities and higher prevalence of social vulnerability factors, they are at higher risk for a range of health consequences.
That is especially consequential during the COVID-19 pandemic and why researchers in the VA Pittsburgh Healthcare System decided to use the veteran population to calculate effectiveness of the two mRNA vaccines granted emergency use authorization to combat the virus.
The goal was to evaluate the short-term effectiveness of the Moderna and Pfizer-BioNTech vaccines in preventing SARS-CoV-2 infection in a real-world setting. The reassuring results were published in Annals of Internal Medicine.1
“Because veterans are at particularly high risk given, their older age and greater burden of comorbidities compared with the general population, these findings should be reassuring,” said primary investigator Adeel Butt, MD, MS, of the Pittsburgh VAMC and Weill Cornell Medical College.
The study looked at all veterans who had testing for SARS-CoV-2 infection between Dec. 15, 2020, and March 4, 2021, and no confirmed infection before that time period. Participants received SARS-CoV-2 vaccination with either the BNT-162b2 (Pfizer–BioNTech) or mRNA-1273 (Moderna) vaccine as part of routine clinical care.
The goal was to gauge the effectiveness of vaccination against confirmed SARS-CoV-2 infection, according to the authors.
Researchers identified 54,360 veterans who tested positive and propensity score-matched them with 54,360 control participants. Among the study subjects, the median age was 61 years, 83.6% were male, and 62% were white. The authors reported that median body mass index was 31 kg/m2 among those who tested positive and 30 kg/m2 among those who tested negative.
Results indicated that, of those who tested positive, 9,800 (18.0%) had been vaccinated, while, among those who tested negative, 17,825 (32.8%) had been vaccinated.
“Overall vaccine effectiveness 7 or more days after the second dose was 97.1% (95% CI, 96.6% to 97.5%),” the researchers pointed out. “Effectiveness was 96.2% (CI, 95.5% to 96.9%) for the Pfizer-BioNTech BNT-162b2 vaccine and 98.2% (CI, 97.5% to 98.6%) for the Moderna mRNA-1273 vaccine. Effectiveness remained above 95% regardless of age group, sex, race, or presence of comorbidities.”
Butt noted in a VA press release that “vaccine effectiveness was numerically similar (though statistically significantly higher) among persons aged 70 years or older compared with those younger than 70 years.”
He added that effectiveness also was similar between Blacks and whites, men and women and those with and without more risk factors, adding that the findings “clearly show the effectiveness of the current vaccines in preventing infection.”
The study did not assess vaccine effectiveness in preventing severe disease and death.
The authors pointed out that the effectiveness study was somewhat limited by using a predominantly male population and by lack of data on disease severity, mortality and effectiveness by SARS-CoV-2 variants of concern and that only a short-term follow-up was included.
Highly Effective
Still, researchers concluded, “Currently used vaccines against SARS-CoV-2 infection are highly effective in preventing confirmed infection in a high-risk population in a real-world setting.”
Background information in the articles noted that the two vaccines have generally shown 94% to 95% efficacy in preventing symptomatic SARS-CoV-2 infection, although the “effectiveness against infection is more difficult to estimate and was lower in the earlier Phase 3 clinical trials.”
The study cited a recent report from Israel indicating 92% effectiveness of the Pfizer vaccine in preventing documented infection and severe disease seven or more days after the second dose. It also discussed another recent report from Qatar, which determined that vaccine was 89.5% effective in preventing infection with the Alpha (previously known as the B1.1.7) variant and 75% effective in preventing infection with the Beta (previously known as the B1.351) strain.
“Other reports from select population groups have noted a sharp decrease in infections among vaccinated persons, although vaccine effectiveness is often not explicitly stated,” the authors wrote. “Real-world data from large, national populations are urgently needed to provide reassurance about the effectiveness of current vaccines.”
As of late July, 51.8% of veteran users had been vaccinated. The VA had provided at least one dose of vaccine to more than 3.6 million people, about 3.2 million of those veterans. The others primarily included employees, family members and other federal beneficiaries.
The VA also has performed about 4.2 million COVID-19 tests and diagnosed 271,127 patients with the infection. Of those, nearly 46,000 have been admitted to VA facilities. As of late July, there were about 350 in-patients with COVID-19 and another 255,053 in some type of convalescence, according to agency statistics.
- Butt AA, Omer SB, Yan P, Shaikh OS, Mayr FB. SARS-CoV-2 Vaccine Effectiveness in a High-Risk National Population in a Real-World Setting. Ann Intern Med. 2021 Jul 20. doi: 10.7326/M21-1577. Epub ahead of print. PMID: 34280332.
