Asymptomatic and symptomatic COVID-19 cases among health care personnel were reduced after vaccination despite surge in infected patients.
Vaccination was associated with dramatic reductions in both asymptomatic and symptomatic COVID-19 cases among health care personnel (HCP), despite a surge in infected patients during the 2020-2021 Winter.
A cohort study at the University of California Irvine (UCI) Health, the sole academic medical center in Orange County, California, was conducted when this sixth largest US county was confronting among the highest infection rates in the Country.Investigators determined that daily HCP cases of COVID-19 fell 55% (from 18 to 8) 1 week after the 2nd vaccination dose.There was an 84% reduction (3 cases) after 2 weeks and 94% (1 case) 3 weeks after full vaccination.
"HCP cases declined when our hospital was still in full surge with an active mobile field hospital and several outpatient areas commandeered for inpatient intensive care unit and non-intensive care unit beds," the investigators reported.
The cases of COVID-19 among over 10,000 HCP in the study were tracked before and after 2-dose vaccination with a Pfizer or Moderna mRNA vaccine through daily screening for elevated temperature and for CDC-defined COVID-19 symptoms; with rapid nasopharyngeal testing if fever or symptoms were present.In addition, asymptomatic bilateral nares testing was provided weekly to HCP randomly selected from invited volunteers.
WIth invited rather than mandated vaccination, 58% of HCP received a first dose within 2 weeks, and 70% within 4 weeks.Twenty-five percent of HCP were invited to receive weekly asymptomatic testing, with approximately 15% of these (500) participating.
The investigators noted that most HCP with COVID-19 who were identified through asymptomatic test (81% (34 of 42) within the 21-week study period reported having symptoms at the posttest interview.Many had dismissed their symptoms as common ailments at the time, but recognized them as COVID-19 in hindsight.
Shruti Gohil, MD,MPH, Division of Infectious Diseases, University of California Irvine School of Medicine, Irvine, CA, and lead author of the study, discussed their findings and current infection control strategies with Contagion.
"Protective measures in the patient care setting did not change significantly after vaccination in healthcare—we maintained most of these regardless of vaccination, and have already begun reinforcing the need to maintain these precautions to all of our staff," Gohil said.
"After CDC and CDPH (California Department of Public Health) guidance came out to de-escalate prevention strategies in non-patient care areas, we did begin incorporating these guidelines," Gohil recounted."However, we are now reverting back to pre-vaccine levels of precaution in those areas as well."
Noting that their data were gathered before the delta variant, Gohil considered the possible different circumstances." Since vaccine efficacy is known to be lower for delta variant, we do expect more 'breakthrough' infections in vaccinated individuals," she said."But this does not equate to vaccine 'failure' since it is 96% effective against severe COVID that could result in hospitalization or death.
"What we are seeing here is very similar to influenza vaccine, which ranges in efficacy from 30 to 60% and yet is highly successful every year in curbing cases nationally and dramatically reducing risk of influenza-related hospitalizations and deaths," Gohil observed.