State reports small number of ‘breakthrough’ COVID-19 cases in fully-vaccinated Alaskans

A person gets tested for coronavirus.
Coronavirus testing at the Ted Stevens Anchorage International Airport on June 22, 2020 (Liz Ruskin/Alaska Public Media)

Alaska’s state health department reported Wednesday that 152 fully-vaccinated residents ended up testing positive for COVID-19 in February and March. 

That’s just one-tenth of one percent of vaccinated Alaskans, said State Epidemiologist Dr. Joe McLaughlin. It’s roughly 2% of infections reported in Alaska since early January. 

“If you’re vaccinated, you really dramatically decrease your risk of infection,” McLaughlin said during a call with reporters. “It’s very, very uncommon to have vaccine breakthrough cases.”

A “breakthrough case” is the term used to describe someone who has tested positive for COVID-19 at least two weeks after their final shot of the vaccine. The cases are being tracked across the country

Louisa Castrodale, an epidemiologist with the state, said the small number of breakthrough cases tallied in Alaska isn’t surprising. The vaccine is extremely effective, she said, but it’s not perfect — no vaccine is.

Studies have shown that the Pfizer and Moderna versions are about 95% effective at preventing COVID-19, while the single-dose Johnson & Johnson vaccine is 66% effective

“The vaccine doesn’t work 100%. So we’re going to see people who get sick with COVID who have been vaccinated,” Castrodale said. “We knew that.”

The goal is to get more Alaskans vaccinated so the state reaches “herd immunity” — a point where enough people are protected from the virus that it no longer spreads easily through the population.

What’s important to note about Alaska’s breakthrough cases so far: About 60% never had any symptoms, said Castrodale.

That’s because vaccinated people who become infected with COVID-19 are less likely to get very sick, compared to those who are unvaccinated. Also, they’re less likely to spread the virus to others, Castrodale said.

RELATED: You’re vaccinated for COVID-19. Now what can you do?

Most of the breakthrough cases were detected during routine testing for travel or work, or before medical procedures. The median age of the Alaskans was 51.

Among the 152 cases, one Alaskan with multiple, long-term chronic conditions was hospitalized, according to the state’s report. Shortly after the positive result, the person took a second test and was negative.

Another Alaskan who was older than 65, with several chronic conditions affecting various organ systems, tested positive for COVID-19 and died about two weeks later, said Castrodale. 

“It’s the reason why we just want to prevent as much COVID as possible, because there are those fragile people who have systems that really can’t take COVID,” she said. 

Castrodale and other health officials on Wednesday underscored that the vaccine is the best protection against the coronavirus. They called on more Alaskans to get vaccinated, not only to protect themselves, but also to drive down the number of coronavirus cases in the state and protect others. 

“The less COVID we have circulating, the less breakthrough cases we’ll see,” said Dr. Anne Zink, Alaska’s chief medical officer. 

State health officials are also asking anyone with COVID-19 symptoms — vaccinated or not — to get tested immediately.

But, vaccinated people without any symptoms of COVID-19 don’t have to go through routine testing, including before and after travel, according to new guidelines this week from the federal Centers for Disease Control and Prevention.

As of Wednesday, about half of Alaskans age 16 and up had gotten at least their first dose of vaccine, according to state data. 

Meanwhile, the number of new COVID-19 cases statewide declined last week. The state reported 1,090 new cases in Alaska, a 3.5% decrease from the week before. Case rates more than doubled in Fairbanks, but dropped in Anchorage, the Matanuska-Susitna region, Juneau, the Northern Southeast and Southwest regions.

RELATED: In Interior Alaska, severe COVID-19 cases surge while vaccinations lag

Reach reporter Tegan Hanlon at or 907-550-8447.

Tegan Hanlon is the digital managing editor at Alaska Public Media. Reach her at or 907-550-8447. Read more about Tegan here.

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