A fully-vaccinated Houston wedding led to 6 Delta variant cases. Did certain vaccines save lives? – Houston Chronicle

https://www.houstonchronicle.com/news/houston-texas/health/article/A-fully-vaccinated-Houston-wedding-led-to-6-Delta-16304205.php


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A couple hosting an outdoor wedding outside Houston in April required full COVID-19 vaccination from all of their guests. It was an open-air event, with 92 people in attendance.

Their happy day turned into a nightmare, though, after one attendee died, two others were hospitalized with severe illness and three others tested positive for the coronavirus. In a pre-print study of COVID-19 Delta variant breakthrough infections among guests who had received the vaccine, Baylor College of Medicine researchers say the newly dominant strain of the virus may pose the highest risk of infection of all the variants spreading worldwide.

The person who died was vaccinated with Covaxin, a shot not authorized for emergency use in the U.S. One of the hospital patients received Covaxin, while another received Pfizer. Both Covaxin recipients had traveled from India for the wedding.

All three people who caught the virus but showed mild symptoms were vaccinated with Pfizer or Moderna’s products.

“All the current data shows robust ability to block serious illness from the Delta variant,” said Tim Farinholt, one of the study’s authors. “It’s not to scare, it’s to remain cautious that the pandemic is not over and to remain vigilant. It’s for people to know just because you’re vaccinated doesn’t mean you can go back to 2019 living.”

A pre-print study has not been peer-reviewed by independent scientists and should not be used to guide clinical practices, researchers said. However, it is a preliminary finding to relay interesting developments and help other scientists determine what to study. Peer review can take two to four weeks.

Unvaccinated individuals make up the majority of COVID-19 hospitalizations and deaths reported in the U.S. in recent weeks, according to infectious diseases specialists. Of the tiny share — less than 3 percent in the Baylor study — who are vaccinated and catch severe infections, most have other comorbidities or are immunosuppressed. One of the patients who contracted severe illness had diabetes and received a monoclonal antibody infusion treatment. The patient who died did not have a chronic illness, but was over 65, an age group at increased risk of serious infections.

All six infected tested positive for the Delta variant. The other three wedding guests who caught COVID-19 and were vaccinated with Pfizer and Moderna had mild symptoms such as fevers, coughs and fatigue. The findings line up with the efficacy rates the pharmaceutical giants promised in their clinical safety trials, said Dr. Pei-yong Shi, a professor of biochemistry and molecular biology at the University of Texas Medical Branch in Galveston who independently reviewed the pre-print at the request of the Houston Chronicle.

“The vaccine didn’t absolutely prevent you from getting infected,” Shi said. “But one of the major benefits is that it keeps you from getting really sick.”

Covaxin, a vaccine developed from inactive coronaviruses, has an efficacy rate of 81 percent, according to BBC News. However, the drug manufacturer came under fire in January after it was cleared for emergency use during its clinical trial phase.

In comparison, Pfizer’s vaccine is 95 percent effective and Moderna’s vaccine is 94 percent effective against the original virus strain. Varying studies have been released on the efficacy of the vaccines and the Delta variant, ranging from 64 percent effectiveness to 88 percent effectiveness.

The pre-print journal article linked Delta, which has mutations in part of the spike protein that could help it strengthen its bond to a cell’s receptors, as the cause of the breakthrough infections. Delta, which some epidemiologists say is 60 percent more transmissible than the original SARS-CoV-2 strain, already makes up more than half of new infections in the U.S.

Houston Methodist researchers earlier this week released findings that the Delta variant could make up 92 percent of all new infections in the coming weeks if it continues at its current rate of spread.

“It’s hard to say if the breakthrough they’re seeing is something that’s a feature of Delta or if this is a thing that happens occasionally. We don’t have data to tell a coincidence from a rare event at this point,” said Ben Neuman, a virologist at Texas A&M.

While the wedding represents just one case study, it’s also notable the event took place in April — long before Delta became the dominant variant in the U.S., U.K., Israel and India, said Joseph Petrosino, one of the study’s co-authors and the director of molecular virology and microbiology at Baylor College of Medicine. The first cases of the Delta variant had been reported in the U.S. and U.K. in mid-to-late April.

Contact tracing showed that none of the infected patients had recently interacted with someone who had tested positive for a different COVID-19 variant.

“The epidemiology combined with the sequencing data suggests the variant was shared amongst the group,” Petrosino said.

Another finding of the study? The two travelers from India likely brought the Delta variant to the wedding.

“It’s unclear whether people can transmit with both doses of the vaccine,” Petrosino said. “It looks like there’s plenty of evidence suggesting that if your vaccine did not elicit significant immune response, which is possible with a single dose and the Delta variant that you can still transmit it.”

Feeling terrible after a second vaccine dose isn’t the only indicator of the strength of a person’s immune system. But studies show mRNA vaccines such as Pfizer and Moderna prompt robust protection in 90 percent of recipients.

Scientists caution against using the study to justify skipping vaccinations. If someone is not fully vaccinated and carries the infection into an undervaccinated community, that could spread the virus even further and cause new variants to mutate.

Vaccines aren’t perfectly efficacious, but they do offer more protection than what the human body starts out with against coronaviruses, said Katelyn Jetelina, an epidemiologist at University of Texas Health Science Center at Houston.

“We need to be careful how we frame the case study and what we take away from it,” Jetelina said.

gwendolyn.wu@chron.com

twitter.com/gwendolynawu


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