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Type “When will we reach” into your web browser, and the rest of the query autofills at lightning speed: “herd immunity.” It’s the question everyone caught up in the COVID-19 pandemic wants an answer to, especially now that every Missourian is eligible for a vaccine. Google is like a tired parent on a road trip—every five minutes fielding an “Are we there yet?” from an impatient, well, everybody.
Herd immunity is the point at which enough people are immune to an infectious disease that it’s difficult for the disease to spread to others. The St. Louis Metropolitan Pandemic Task Force estimates that the greater St. Louis region could reach this point by mid-July. But even with herd immunity, worries over COVID-19 won’t disappear overnight.
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African family get vaccinated at home during pandemic times.
First up: children. There’s no hard-and-fast rule regarding how many people need to be vaccinated for us to reach herd immunity, but research suggests it’s at least 75 percent of a population. But because health experts have differing ideas about what constitutes a herd immunity threshold, they offer contrasting views as to whether it can be truly reached if children are not vaccinated. (U.S. trials are underway to determine the safety and efficacy of COVID-19 vaccines in children.)
“The continued exposure that parents and teachers will experience will continue to challenge herd immunity,” says Enbal Shacham, professor in the College for Public Health and Social Justice at Saint Louis University. “That is why we need adults to vaccinate as soon as they can, particularly parents and teachers, as their exposure to children is most concentrated.”
Another question: Once a person has been fully vaccinated against COVID-19, how long does immunity last?
Dr. Rachel Presti is a Washington University associate professor of medicine and medical director of its Infectious Diseases Clinical Research Unit. To determine how long immunity lasts, Wash. U. researchers are monitoring COVID-19 vaccine trial participants for two years, looking at immunity and illness. “We are also doing detailed immunologic studies in a group of research participants who were vaccinated under the Emergency Use Authorization Act,” Presti says. She believes that a booster shot will likely be needed but not necessarily annually.
Shots and Stats
As of press time, 877, 461 Missourians had received two vaccines against COVID-19. That’s 14 percent of the state’s population.
People are ready to safely gather. See a movie without renting the entire theater. Go to a Cardinals game and sit elbow to elbow with strangers. Hug a loved one. Hug anyone. They understandably want definite answers as to what activities they should or should not engage in while awaiting herd immunity, as well as after we reach it. “There is not a yes or no answer about when people can feel comfortable safely going to a movie, or to a bar, or to a restaurant,” says Dr. Steven Lawrence, a Wash. U. infectious diseases physician at Barnes-Jewish Hospital. Such decisions, he says, involve the risks people—even if they are all vaccinated—are willing to take. Lawrence is referring to the fact that although all COVID-19 vaccines offer proven protection, such protection is not 100 percent.
Looking ahead, Lawrence says he understands that people want to return to “normal,” but, because of the relative newness of the virus and ongoing studies, he says, “We may want to look at a ‘new normal’ rather than the normal we knew before COVID-19.”
MORE TO KNOW
Vary Scaries
LOCAL RESEARCHERS ARE MONITORING THREE FAST-SPREADING COVID-19 VARIANTS.
Viruses are constantly changing, and this includes SARS-CoV-2. A state analysis of the Coldwater Creek wastewater system in St. Louis County revealed the presence of viral strands with mutations typically associated with the B.1.1.7 variant, originating in the United Kingdom. New research from the Washington University School of Medicine indicates that three fast-spreading new variants—from South Africa, the U.K., and Brazil—can evade antibodies that fight the original form of the virus that sparked the pandemic. How worried should we be?
“There’s wide variation in how much antibody a person produces in response to vaccination or natural infection,” says Dr. Michael S. Diamond, a Washington University professor of molecular microbiology, pathology, and immunology. “Some people produce very high levels, and they would still likely be protected against the new worrisome variants. But some people, especially older and immune-compromised people, may not make such high levels of antibodies. Will we see vaccines lose efficacy and drug resistance merge? I hope not. But it’s clear we will need to continually screen antibodies to make sure they are still working as new variants arise and spread and potentially adjust our vaccine and antibody treatment strategies.”
