UCSF Grand Rounds: The fourth surge, delta variant, boosters and more

UCSF Grand Rounds moderator Dr. Bob Wachter hoped we would be over the worst of the pandemic when the speaker series took a break for the summer. “But clearly that has not been how the summer has gone,” he said, bringing back three UCSF experts Thursday to discuss the pandemic’s fourth surge, the Delta variant and boosters.

The current state

The United States and California have been in a fourth surge since May, running more than 140,000 cases per day and 10,000 cases per day, respectively, according to Dr. George Rutherford, UCSF professor of epidemiology. Though case rates have “clearly turned down” in California and have “seemingly turned down” nationally, Rutherford cautioned against assuming the worst was over. He cited repeated surges in the United Kingdom despite their 65 percent vaccination rate; meanwhile, the United States is at 53 percent full vaccination. 

“We are at risk for this happening, and it’s going to take some concerted effort to keep it from not happening,” he said, referring to another Delta surge.

In the United States, cases are concentrated in the South and Southeast, and extend into the lower midwest and intermountain west. Cases in Florida are dropping, but Rutherford noted that it is unclear how flooding and hurricanes will affect Covid-19 in the Gulf Coast.

What is known, however, is that this surge has affected children. Data from the U.S. Centers for Disease Control shows a surge of covid for those aged 0 to 17 years in August.

Some 65 percent of California’s population has received at least one vaccine dose. The Bay Area “is doing quite well,” with an effective reproduction number (the number of people who can be infected at any time) of less than 1 in most counties, and a test positivity rate of 4.5 percent, which Rutherford said is decreasing. San Francisco had 70 new cases last week, with 79 percent of the city fully vaccinated. 

“The variant to rule them all”

The delta variant “has completely overwhelmed everything else, and it’s not budging,” Rutherford said.

There has also been mixed evidence of declining vaccine efficacy as well as mixed evidence of breakthrough infections, which he said is likely to prompt federal action.

One University of California at San Diego study published in the New England Journal of Medicine found a drop in vaccine efficacy among healthcare workers, from 94 percent in May to 66 percent in June. However, data indicates that most cases and hospitalizations persist among the unvaccinated, with Los Angeles County data showing unvaccinated individuals have 4.9 times higher rates of covid and 29.4 times higher rates of hospitalizations due to covid.

UCSF professor of medicine Dr. Monica Gandhi noted that natural immunity from infection is a large factor in decreasing delta surges, as evidenced by waning surges in Missouri, where there are lower vaccination rates and a ban on mask mandates.

Dr. Peter Chin-Hong, UCSF professor of medicine, agreed. “Natural immunity has been underestimated. Maybe it’s not as sexy or it’s kind of taboo to talk about it.”

Though discussion of the mu variant has been increasing, Gandhi and Chin-hong both believe delta will win out, with Gandhi calling delta “the variant to rule them all.”

Boosters

The United States is considering recommending a third dose to those who received mRNA vaccines. There already exists a booster recommendation for solid organ transplant recipients and immunosuppressed patients, due to non-response to the vaccine among some of those individuals. Chin-Hong said that 50 to 70 percent of people who are immunocompromised may not respond to the vaccine, even after a third shot.

However, the question of waning immunity has prompted discussion about a third dose for the general population six to eight months after the second dose. This rollout of the third dose could  begin on Sept. 20, according to Rutherford. The San Francisco Department of Public Health already offers mRNA boosters to those who received the Johnson & Johnson vaccine, which Chin-Hong said is a good idea if you are over 60.  

Gandhi questioned the need for boosters in the United States to prevent mild disease when a shocking two percent of the residents in Subsaharan Africa are vaccinated. She believes people should mask up, and that we should examine the data for breakthrough infections to sort out who is most prone to illness. Global vaccine equity, she said, is a public health imperative. 

Rutherford instead highlighted what he called “enlightened self-interest.”

 “We have a border with three million people who live on it, who are all unvaccinated,” he said. “That would strike me as something that would be within our purview, to want to take care of that little problem before we start passing out third doses to people who don’t really need them.”

Chin-Hong has mixed feelings about boosters, noting that lots of other vaccines require them, but that “everything looks good right now” regarding current data. There appears to be a slight waning of severe disease, death, and hospitalization protection among the older population in Israel, but he said this data has not been peer reviewed. 

Traveling, masking and herd immunity

The biggest question many people have today, Chin-Hong said, is about the safety of traveling. He encouraged precautions while traveling, and said flights are okay. Gandhi recommended wearing higher-grade masks, such as KN95s, when flying, or using a cloth mask paired with a surgical mask. “Not all masks are equal,” she said, citing a preprint study from Bangladesh that found that those over 50 wearing surgical masks were better protected from symptomatic infection than those wearing cloth masks. 

While many are discussing the UK’s lack of masks in schools, Chin-Hong reminded viewers that the UK is outperforming the United States in many other strategies, such as testing and contact tracing. Gandhi said San Francisco schools have “really low rates of transmission,” according to Department of Public Health data, but she still suggested implementing an antigen “test-to-stay” strategy in SF Unified School District to keep exposed children in school. 

Chin-Hong believes school cases have been so low because there is a “bigger wall of immunity around the kids under 12 in SF.” But will this wall among children and the general population reach herd immunity levels? Rutherford predicts that it will. “It’s going to take some substantial amounts of pediatric vaccination to get there,” he said, but he believes we are “pretty close.” 

Chin-Hong was not as certain. “Borders are so porous, and there are people moving in and out of San Francisco all the time.” However, “If anybody’s going to do it, we are going to do it in the Bay Area,” he said. 

See our previous Grand Rounds coverage here.