Why COVID-19 cases haven't seen sharp drop despite spike in vaccinations

Variants and low vaccination numbers are factors.

April 27, 2021, 5:12 AM

States across the country are reporting large numbers of people getting their coronavirus shots, and according to the U.S. Centers for Disease Control and Prevention, nearly 95 million doses have been administered over the last month alone.

Regardless, the number of newly reported COVID-19 cases in the U.S. has not decreased dramatically, in fact, there is a seven-day average hovering around 60,000 cases a day, according to CDC data.

But Dr. John Brownstein, an epidemiologist at Boston Children's Hospital and an ABC News contributor, said there is no immediate reason for alarm, since the country still has a ways to go before we see a major impact from the vaccines.

Medical workers provide vaccines against COVID-19 at Gillette Stadium in Foxborough, Mass., Feb. 1, 2021.
Joseph Prezioso/AFP via Getty Images, FILE

"We're getting there," Brownstein said. "What's important to remember is we see these high level of metrics of vaccine coverage, there will be some level of variability from different parts of the country."

Brownstein noted that some states are seeing declines in their case numbers, but a few, like Michigan and Pennsylvania, are showing increases, and thus affecting the overall national data.

He said there are a number of factors behind those new cases, including more transmissible COVID-19 variants. Nearly 60% of new COVID-19 cases in Michigan are of the B 117 variant from the U.K., according to CDC data.

So far, studies have shown that mRNA vaccines are effective against all known variants, including B117.

Brownstein noted that the most recent data has shown a small decline in cases, with the seven-day average dipping below 54,000 on Saturday, according to CDC data.

"We don't have a steep of a decline compared to the rise in vaccination numbers, but it is still much below that 60,000 average we had a few weeks ago," he said.

People line up to receive rapid COVID-19 tests on Feb. 17, 2021, in Immokalee, Fla.
Spencer Platt/Getty Images, FILE

Even though the country has opened up vaccine eligibility to anyone over the age of 16, Brownstein noted that there are still hundreds of millions of Americans who haven't received their shot and the tide will change as more people get their doses.

As of Monday, more than 140 million people, roughly 42.5% of the U.S. population, have received one vaccine dose, and more than 95 million people, roughly 29% of the total population, are fully vaccinated, according to the CDC.

"In Israel, when they had 45% fully vaccinated, the cases started to plummet," Brownstein said.

Brownstein said that patients who haven't scheduled their shots should do so as soon as possible so that the case numbers can go down and Americans are more protected against the variants.

He recommended that those who are still waiting to get their shots adhere to health guidelines by socially distancing, avoiding big crowds indoors and wearing masks.

"While it may be tempting to say, 'Even though I'm not vaccinated I can benefit the same way as others who have gotten vaccinated,' that's not true," he said. "We cannot change things until everyone is fully vaccinated."

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