COVID Vaccines Put to the Test in Essential Workers

 COVID-19 vaccination with Pfizer or Moderna mRNA vaccines was effective in essential workers, preventing infection and reducing the severity of breakthrough illness, a real-world study found.

Adjusted vaccine effectiveness was 91% (95% CI 76-97%) for full vaccination (defined as 14 days or more after dose two) and 81% (95% CI 64-90%) for partially vaccinated workers (defined as less than 14 days after dose two), reported Mark Thompson, PhD, of the CDC in Atlanta, and colleagues.

Moreover, risk of febrile illness in partially or fully vaccinated participants with breakthrough illness was 58% lower (OR 0.42, 95% CI 0.18-0.98), and time spent sick in bed was about 2 days shorter compared to their unvaccinated colleagues, they wrote in the New England Journal of Medicine.

They added that while efficacy of the vaccine in preventing symptomatic infection is well known from the clinical trials, there are less data on secondary benefits, such as potential reductions in COVID-19 severity, viral RNA load, and how long viral RNA can be detected.

The HEROES-RECOVER network included healthcare personnel, first responders, and other essential workers in Arizona, Florida, Minnesota, Oregon, Texas, and Utah from December 2020 to April 2021.

Participants completed electronic surveys on sociodemographic and health characteristics at enrollment, and monthly surveys about potential exposure to SARS-CoV-2, as well as use of face masks and other personal protective equipment (PPE), including time spent using PPE. They also reported any COVID-19 symptoms they experienced, including their severity and duration.

Febrile illness was defined as fever, feverishness, chills, or a measured temperature higher than 38° C (1oo.4°F). Participants provided a weekly nasal swab and saliva specimen, regardless of symptom status. Vaccination status was reported by participants through electronic and telephone surveys, as well as direct uploads of images of their vaccination cards.

Primary outcome was time to RT-PCR-confirmed SARS-CoV-2 infection in vaccinated versus unvaccinated participants, with secondary outcomes of viral RNA load, frequency of febrile symptoms, and duration of illness in patients with COVID-19 infection.

Overall, 62% of participants were women and 72% were ages 18 to 49. They were mostly (86%) white, and 69% had chronic conditions. A third of participants were nurses or other allied healthcare personnel and 26% were other essential or frontline workers, while 20-21% were primary healthcare providers and first responders.

In total, 3,179 participants received at least one dose of mRNA vaccine and of those, 84% received both doses. There were also 796 unvaccinated participants.

SARS-CoV-2 infection was detected in 204 participants, five of whom were fully vaccinated, 11 who were partially vaccinated, and 156 who were unvaccinated; 32 whose vaccination status was unknown were excluded. Of 81 sequenced virus samples, 10 were variants of concern.

Interestingly, viral RNA was detected for less than 1 week in 75% of fully or partially vaccinated participants, but was detected for more than 1 week in 72% of unvaccinated participants.

Among participants with RT-PCR confirmed infection, 25% of fully or partially vaccinated participants reported symptoms versus 63% of unvaccinated participants. Vaccinated participants also reported about 6 fewer total days of symptoms.

Limitations to the data included the fact that an 81% vaccine effectiveness estimate for partial vaccination is based on a median of 22 partially vaccinated days. That could overestimate vaccine effectiveness if infections were not detected in vaccinated participants, due to either reduction in viral RNA load or sensitivity of PCR assays. Also, the researchers were not able to complete genetic sequencing for all viruses.

Disclosures

The study was supported by the National Center for Immunization and Respiratory Diseases and the CDC.

Thompson disclosed no relationships with industry. Co-authors disclosed other government funding and various ties to industry.

Primary Source

New England Journal of Medicine

Source Reference: Thompson MG, et al "Prevention and Attenuation of Covid-19 with the BNT162b2 and mRNA-1273 Vaccines" N Engl J Med 2021; DOI: 10.1056/NEJMoa2107058.

https://www.medpagetoday.com/infectiousdisease/covid19vaccine/93378