New Research Details SARS-CoV-2 Vaccine Protection Among Veterans

A recent study of US veterans reveals that although vaccination did remain protective against SARS-CoV-2 infection, that protective effect trailed off as the Delta variant emerged and spread across America.

Findings published November 4 in Science reveal that vaccine effectiveness against infection dropped from about 88% to roughly 48% from February 2021 to October 2021, a timeframe that encompassed the emergence of the Delta variant. 

The endurance of vaccine effectiveness against infection depended upon vaccine type. For example, the decline was most pronounced for the Johnson & Johnson (J&J) Janssen vaccine, with protection dropping to about 13%. 

In May 2021, the Centers for Disease Control and Prevention moved from monitoring all breakthrough infections to focusing on hospitalized or fatal cases, the researchers explained. While some data on vaccinations, infections, and deaths are gathered via local health departments, that information can be out of date and challenging to combine at a national level. 

To address this apparent gap in national data on vaccine breakthroughs, lead author Barbara Cohn, PhD, of the Public Health Institute and her colleagues took a closer look at SARS-CoV-2 infection and deaths in relation to vaccination status, considering over 780,000 US veterans in all.

“Patterns of breakthrough SARS-CoV-2 infection among vaccinated veterans show a worrisome temporal trend, overlapping with the emergence of Delta as the dominant variant in the US in July 2021,” the researchers noted. Whereas other research has shown high vaccine effectiveness against infection and death in veterans during the vaccine rollout through mid-March 2021, these “results suggest vaccines are less effective in preventing infection associated with the Delta variant.”

While breakthrough infection did increase the risk of fatality, protection against death remained high for all vaccine types in veterans who became infected during the Delta surge. From July 2021 to October 2021, vaccine effectiveness against death for those under the age of 65 was about 84% for Pfizer-BioNTech, 82% for Moderna, and 73% for J&J/Janssen. In veterans aged 65 years and older, protection was 76% for Moderna, 70% for Pfizer-BioNTech, and 52% for J&J/Janssen.

Compared to unvaccinated veterans, researchers indicated that fully vaccinated veterans had a far lower risk of death following infection. According to their findings, unvaccinated individuals remained at the highest risk of infection, severe disease, and death. 

Authors wrote, “Vaccines remain the most important tool to prevent infection and death,” adding that they should be used along with additional measures like social distancing, masking, and hand washing—for the vaccinated and unvaccinated alike. 

“It is essential to implement public health interventions, such as strategic testing for control of outbreaks, vaccine passports, employment-based vaccine mandates, vaccination campaigns for eligible children as well as adults, and consistent messaging from public health leadership in the face of increased risk of infection due to the Delta and other emerging variants,” researchers concluded.

The study reveals that vaccines do work, and they do prevent people from dying, said the study’s senior author Art Wallace, MD, PhD, a professor of anesthesiology and perioperative care at the University of California–San Francisco and chief of anesthesia service at the Veterans Affairs Medical Center in San Francisco. 

“People who got vaccinated were less likely to die than people who were unvaccinated,” Dr Wallace told Veterans Health Today. However, another big takeaway of this research is that the vaccine efficacy was slowly wearing off over time. And as the Delta variant surged during the summer months, he said, “it really stopped being adequate.” 

The variant’s higher viral load likely plays a significant role.

“The Delta variant is sneaky. It figured out how to make 1000 times more viral particles,” Dr Wallace said. So instead of having x particles sprayed in someone’s face when you cough, roughly 1000x viral particles are sprayed, which overwhelms the vaccine.  

Although most people tend to bounce back within a matter of weeks, he pointed out that not everyone experiences a quick or easy road to recovery. In addition to those who die, many others experience lingering symptoms long after being infected with the virus that causes COVID-19. 

As such, he emphasized the importance of continuing to use an array of preventative measures. Get vaccinated, get boosted, and wear a mask, in addition to washing hands and maintaining social distancing. It is easier to solve the problems posed by COVID-19 by taking action to avoid getting it in the first place, Dr Wallace added.

Reference:
Cohn BA, Cirillo PM, Murphy CC, Krigbaum NY, Wallace AR. SARS-CoV-2 vaccine protection and deaths among US veterans during 2021. Science. 2021. doi:10.1126/science.abm0620