Implementation of ventilation standards with at least five clean-air changes per hour, regular COVID-19 testing, the use of personal protective equipment (PPE), and the universal wearing of respirators played a crucial role in preventing most SARS-CoV-2 transmissions in a California healthcare system from 2020 to 2022, according to a study published in Clinical Infectious Diseases.

The study, conducted by researchers from the University of California (UC), utilized electronic health records and movement data of patients and healthcare workers (HCWs) in the UC-San Diego Health system. The team analyzed a total of 12,933 viral genomes from 35,666 infected individuals, including both patients and HCWs, between November 2020 and January 2022.

HCWs in the healthcare system were required to wear N95 respirators, eye protection, gowns, and gloves when providing direct care to COVID-19 patients. They were also advised to wear KN95 or N95 respirators in all areas of the hospital, even non-patient-care spaces. Unvaccinated HCWs underwent COVID-19 testing twice weekly, while vaccinated HCWs were tested weekly during periods of increased community transmission. Each HCW completed a daily symptom survey and was referred for testing if they reported any positive symptoms or exposure.

Patients, on the other hand, were tested upon admission and on the third day of hospitalization. They were instructed to wear masks when within 6 feet of another person, although compliance was noted to be inconsistent. Due to limited negative-pressure rooms, not all COVID-19 patients were placed in these rooms, and the doors to their rooms were often left open for direct observation.

The study found that out of the 5,112 SARS-CoV-2 viral samples sequenced from the second and third waves of the pandemic, 34 genetic pairs (12%) were genetically linked, with 19 attributable to household transmission and 14 to healthcare spread. During the Omicron period in December 2021 and January 2022, there was a significant increase in COVID-19 cases among HCWs, with 1,376 testing positive, representing an 800% increase compared to the previous two months. At the peak of the wave, up to 257 HCWs tested positive daily. Among the genetic sequences analyzed during this period, 120 related pairs among 32 clusters were identified, with 10 clusters likely being healthcare-related.

The study also revealed that transmission was more likely to occur in shared spaces within the older Hillcrest campus as compared to the newer La Jolla campus, which predominantly had single-occupancy patient rooms. The Hillcrest campus accounted for a higher number of transmission events and a higher rate of transmissions per 1,000 admissions compared to the La Jolla campus.

However, the researchers emphasized that most transmission of the virus occurred outside of the healthcare setting, particularly in the community and between households, or when universal masking was not followed. They highlighted the importance of ventilation and air exchanges in all spaces, as well as the support for single-occupancy rooms to further enhance infection prevention protocols in healthcare facilities during future respiratory virus pandemics.

The study's findings indicate that strict adherence to ventilation standards, regular testing, proper use of PPE, and the universal wearing of respirators were effective in preventing the majority of SARS-CoV-2 transmissions within the California healthcare system. These measures, combined with efforts to address lapses in adherence and enhance mitigation measures, can play a crucial role in controlling the spread of respiratory viruses in healthcare settings.

It is worth noting that despite hundreds of HCWs becoming infected during the peak of the Omicron wave, the study found no evidence to suggest that they were more likely to acquire the virus within the hospital system.

Further research and ongoing implementation of effective infection-control measures will be essential in ensuring the safety of healthcare workers and patients during future pandemics.