San Antonio Express-News (Sunday)
Is achieving herd immunity still feasible?
Some experts say focus should be on getting as many people vaccinated as soon as possible
Imagine the coronavirus pandemic is a zombie apocalypse. Swarms of the undead are coming and your best bet for survival is to build a big, sturdy barrier to keep the zombies at bay and away from you and your loved ones.
In this analogy, the barrier is made up of every single person who is immune to COVID-19 — whether because they are vaccinated or because they were previously infected.
“If there’s a gap in that fence, a zombie can come in and then infect your entire population,” said Joanne Turner, executive vice president for research at Texas Biomedical Institute and an infectious disease scientist.
“If one person in that fence decides not to get vaccinated because they don’t believe in it, then you’ve already made a gap. As long as that barrier is 100 percent intact, then nothing can get through.”
The zombie apocalypse is how she likes to explain herd immunity — the point when most of the population is immune. It’s also known as population immunity and community immunity.
Dr. Junda Woo, medical director of San Antonio Metropolitan Health District, said she doesn’t use a barrier wall analogy, mostly because it reminds her of the politics surrounding the U.S.-Mexican border wall.
Woo prefers an animated video produced by the Texas Medical Association to explain the concept.
People wearing raincoats in the video have been vaccinated or are otherwise immune to the virus because of prior infection. So as the coronavirus pours down, they stay dry.
If there are enough people vaccinated, it’s like there is a big umbrella covering the entire group and the people without raincoats can stand underneath it and be shielded from the rain.
There’s a scene in the 2011 film “Contagion” where Kate Winslet’s character explains the reproductive rate of a deadly virus called the R-naught.
The rough math she writes on a dry erase board is the infection rate — the average number of people infected by just one sick person. The higher the number, the harder it is to slow down the transmission of the virus.
That part is less Hollywood and more reality at a time when people sought to learn more about pandemics, which is probably why the film was trending on streaming services last summer just as quarantines were in full effect and many Americans shifted to remote work and overseeing their children’s virtual education.
For many people, herd immunity symbolizes the promise of returning to normalcy. And as the virus continued to sweep across the nation, the term was often used to describe a sort of end goal.
The end of the pandemic means it’s safe to fully reopen schools, movie theaters and other large public gathering places, paving the way for concerts, graduations and sporting events.
But with virus variants circulating and people refusing to get the vaccine, refusing to practice social distancing or wear masks, plus the portion of the population not yet eligible for the vaccine — is the goal of reaching herd immunity still possible?
Local infectious disease specialists aren’t so sure, but for the good of the community, they certainly hope so.
SARS-CoV-2, the specific coronavirus that causes the COVID-19 disease, already has killed more than 3 million people across the globe, including more than half a million Americans and at least 3,300 Bexar County residents.
A moving target
Reaching herd immunity has always been considered a moving target among public health experts.
“We don’t know exactly what that threshold is. Some say it lies somewhere between 70 and 96 percent,” said Woo. “Honestly, we don’t know yet.”
Turner, at Texas Biomed, says she thinks once San Antonio reaches around 50 percent of people vaccinated, the number of infections and hospitalizations should steadily decline. But to really eradicate COVID-19, “we need to get up to much higher proportions.”
No one really knows what the percentage of vaccinated individuals needs to be before a community can turn the tide on coronavirus infections, severe illness and deaths.
While some parts of the country, including Texas, have seen respite from surges of COVID-19 hospitalizations and deaths, 38 states are reporting an increase in infections, further straining health care workers on the front lines.
Earlier this month, Dr. Anthony Fauci, the nation’s chief medical adviser on the disease, said at a White House briefing that he no longer wants to focus on the elusive goal of herd immunity. Rather, he believes everyone should be concentrating on getting more people vaccinated as quickly as possible.
Over the past four months, 87 million Americans have been fully vaccinated with one of the three vaccines approved for emergency use by the U.S. Food and Drug Administration.
In Texas, more than 45 percent of residents have been vaccinated with at least one dose, according to state data.
COVID-19 vaccines are
safe and effective, but there is still a segment of the U.S. population that does not intend to get one.
San Antonio vaccine providers are starting to see demand wane and have shifted from scheduling appointments weeks out to allowing walk-up patients without an appointment.
WellMed, which has vaccinated more than 175,000 residents since Jan. 11, is consolidating its two vaccination clinics to a single location at Elvira Cisneros Senior Community Activity Center on 517 S.W. Military Drive.
It’s for all 16 and older
The Centers for Disease Control and Prevention recommends that everyone 16 years and older get the vaccine. Not just healthy people and those with underlying health conditions that pose additional risks if the virus is contracted, but also people with weakened immune systems, those with autoimmune conditions and pregnant women.
“Part of the problem was this was so poorly articulated by the previous administration,” says Dr. Carlos Roberto Jaén, an epidemiologist, physician and chair of family and community medicine at UT Health San Antonio.
Jaén says his own daughter is pregnant and she got vaccinated early on because she’s a labor and delivery nurse. Pregnant women are at increased risk for severe illness from COVID-19 compared with nonpregnant women.
Fears that the vaccines were somehow not properly tested because they were approved so quickly are unfounded, experts repeat time and time again.
The vaccines made by PfizerBioNTech, Moderna and Johnson & Johnson’s Janssen have been evaluated in tens of thousands of participants in clinical trials. They underwent strict monitoring by federal regulators, who continue to evaluate the performance of the vaccines.
On April 13, government officials recommended injections of the J&J vaccine be paused while health agencies investigate rare blood clotting disorders that occurred in six women among the 7 million who received the shot. U.S. health officials lifted the pause Friday.
Fauci, said he expects J&J shots will resume this week.
How long does it last?
There’s still a question of how long the vaccines provide protection from the disease.
Scientists don’t actually have an answer for that. And they don’t know how long immunity lasts for those who have recovered from infection.
Vaccine makers say it’s likely annual booster shots will be needed, much like what’s required for the flu.
Dr. Jason Bowling, an infectious disease specialist at UT Health San Antonio and University Health, said people should remain vigilant even after they’ve been vaccinated.
It takes about two weeks for the body to build protection after vaccination, so a person could get sick if they catch it during this time period.
And a small number of people who receive the full vaccine may still contract the coronavirus, according to the CDC, which is investigating these “vaccine breakthrough cases.”
Bowling said to reach herd immunity this year, children will need to be vaccinated.
That could happen as early as this summer for children between the ages of 12 and 15. Drug companies already are studying the effectiveness of the vaccines on that age group. Still younger children could be eligible for the vaccines by early 2022.