New vaccine study shows Moderna outperforming Pfizer in preventing breakthrough cases

Posted at 5:13 PM, Aug 13, 2021
and last updated 2021-08-13 19:31:38-04

MILWAUKEE — A new Mayo Clinic study suggests the Moderna vaccine is performing far better than Pfizer when it comes to breakthrough infections.

Mayo Clinic in Minnesota followed tens of thousands of vaccinated people for the past six months. While they found one vaccine outperformed another at preventing infections, researchers say all of the approved vaccines show strong results in minimizing hospitalizations.

Results from Mayo’s study show Moderna’s vaccine was 76 percent effective at preventing infections last month, a 10 percent decrease compared to earlier in the year before the Delta variant spread. Hunter Skluzacek received Moderna shots several months ago.

“I think it's reassuring to know that,” he said.

The retrospective study of the Pfizer vaccine shows its effectiveness in preventing new coronavirus cases fell to 42 percent in July. Jesse Perez is disappointed to see the results after seeking out Pfizer shots in particular.

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"It's just frustrating knowing that you go through all the time to schedule that, to go through and get that and now it's not as effective against the Delta variant,” he said.

Before the virus mutated, clinical trials found Pfizer and Moderna’s effectiveness to be nearly identical at about 95 percent. Dr. Hashim Zaibad offers both vaccines at Hayat Pharmacy in Milwaukee.

"I was a little bit surprised,” he said about the study’s results. “Pfizer has been a lot more popular in our area."

Nearly 3.3 million doses of Pfizer have been administered so far in Wisconsin, which is about 800,000 more than Moderna. That’s in part because Pfizer is the only vaccine currently approved for kids ages 12-17.

Dr. Zaibak says he’s already seen people come in this week referencing the Mayo Clinic study and requesting Moderna.

“I think there's going to be a lot more people who are not vaccinated yet who are going to come to us and say 'I do want the Moderna versus the Pfizer,'” he said.

Dr. William Hartman is UW Health’s lead investigator for COVID-19 vaccine trials. He says both Moderna and Pfizer use the same technology called ‘mRNA’, but there is one difference.

"The size of the Moderna vaccine suggests that perhaps there's more mRNA within the lipid coding and so it may deliver a quote unquote higher dose of vaccine or mRNA to produce the spike protein, so you may see slightly higher antibody levels because of that,” he said.

Dr. Hartman stresses both vaccines remain very effective in preventing hospitalizations. Mayo Clinic’s study found Moderna’s vaccine to be 81 percent effective in minimizing hospitalizations in July. The study shows Pfizer was 76% in preventing hospitalizations last month.

"It's predominately unvaccinated people that are ending up with serious illness and hospitalization, and unfortunately still dying from COVID-19,” he said.

Dr. Hartman encourages more study participants as the CDC weighs the need for everyone who’s already vaccinated to get a booster shot.

"Especially in this day of the Delta variant, to really have us take a look at it and see, do we need boosters number one, and if we do need boosters, do we need to do it with the Moderna vaccine,” Dr. Hartman said.

Pfizer says its studies have found a decline in efficacy against symptomatic infection over time, from 95% within the first two months after getting vaccinated, to low-to-mid 80s four to six months post second dose. Pfizer is pushing to offer its own boost shot to provide better protection against variants.

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