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By Gary Evans, Medical Writer
With the Centers for Disease Control and Prevention’s recent approval of a third COVID-19 shot for the immune compromised, evidence strongly suggests healthcare workers should be the next group to receive the vaccine booster.
A recently published study from Israel showed healthcare workers with breakthrough infections were biologically capable of transmitting to patients, but did not. In addition, almost 20% of the fully vaccinated healthcare personnel with breakthrough infections developed long COVID symptoms (> 6 weeks).
The Israeli researchers reported that the Alpha (B.1.1.7) variant was identified in 85% of cases, similar to its prevalence in the community.
The Delta B.1.617.2 variant – which is responsible for the vast majority of U.S. cases – is twice as contagious as the preceding variants Alpha and Beta (B.1.351), the CDC notes.
The Delta surge is driving cases nationally, with those hospitalized still primarily the unvaccinated. “In late June, our 7-day moving average of reported cases was around 12,000,” the CDC reported. “On July 27, the 7-day moving average of cases reached over 60,000.”
Shockingly, the latter case rate looks more like the toll of infections seen before the COVID-19 vaccines were widely available, the CDC warned.
Delta is the first variant the CDC says can potentially infect others after breakthrough infection. Although the Israeli researchers found some markers for infectivity, no secondary cases occurred with the Alpha strain. That situation may change in the United States, where the CDC says there has already been breakthrough transmission in the large outbreak in Provincetown, MA.
Given its known enhanced characteristics, Delta arguably could cause more breakthrough infections in healthcare workers, make them individually more infectious, and give some percentage of them long COVID. There is also concern that healthcare workers are reaching the immunity waning point of the two mRNA vaccines, as they were among the first to be vaccinated in the pandemic.
“We characterized all COVID-19 breakthrough infections among 39 fully vaccinated healthcare workers during the 4-month period after the second vaccine dose and compared the peri-infection humoral response in these workers with the response in matched controls,” the Israeli researchers reported. “We found a low rate of breakthrough infection (0.4%). Among the 39 workers who tested positive for COVID-19, most had few symptoms, yet 19% had long COVID-19 symptoms (> 6 weeks)."
Of concern, most of the infected healthcare workers had “N gene Ct values” that suggested they had been infectious at some point. These workers included some who had been asymptomatic and thus who had infections that would not have been detected without the investigators rigorous screening and follow-up of even minor exposures.
“This factor suggests that at least in some cases, the vaccine protected against symptomatic disease but not against infection,” the authors report. “However, no secondary infections were traced back to any of the breakthrough cases, which supports the inference that these workers were less contagious than unvaccinated persons, as has been reported previously.”
The researchers did a case-control experiment matching healthcare workers with breakthrough infection who had antibody titers obtained within a week before SARS-CoV-2 detection (peri-infection period) with four to five uninfected controls. The 39 breakthrough cases were found among 1,497 fully vaccinated healthcare workers.
Asked about the implications of the Israeli study and when healthcare workers may receive a booster, a CDC press officer sent the following reply:
"We have been reviewing the science and data on a near daily basis to evaluate whether or when boosters may be needed," said Kristen Nordlund, special assistant to the director of communications at the CDC. "As we have been saying, boosters would probably be needed. We will be announcing more detailed plans soon, so we’ll have more to share then. This will all be done in accordance with independent FDA and CDC review and recommendations."
For more on this story, see the next issue of Hospital Employee Health.
Gary Evans, BA, MA, has written numerous articles on infectious disease threats to both patients and healthcare workers. These include stories on HIV, SARS, SARS-CoV-2, pandemic influenza, MERS, and Ebola. He has been honored for excellence in analytical reporting in newsletter journalism five times by the National Press Club in Washington, DC.