A patient receives an injection of the Oxford/AstraZeneca COVID-19 vaccine.
BEN STANSALL/AFP via Getty Images
  • Covid-19 vaccines are extremely effective, but a rare few fully vaccinated people have got sick.
  • "Breakthrough" infections are typically mild and may be less contagious than regular cases.
  • To completely prevent infections, more of the population needs to get vaccinated.
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Karlee Camme was supposed to see her grandparents for the first time in over a year. Everyone was fully vaccinated and ready to go, but two days before the visit, she lost her ability to taste and smell.

Camme, 24, had been vaccinated with the Johnson & Johnson vaccine a month before. But it turns out she had a mild case of Covid-19.

Looking back, she realised the runny nose and heavy tiredness she'd experienced earlier in the week may have been early symptoms. It was only the loss of taste and smell that signalled it was anything more than a common cold, leading Camme to get a Covid test.

The Covid-19 vaccines have been extremely successful at preventing serious illness that could lead to hospitalisations and deaths. But no existing vaccine is 100% effective at preventing infection, Dr Lisa V Adams, associate dean for global health at Dartmouth College, told Insider.

"We know there are and will be some breakthrough infections in individuals who are vaccinated - at least until we get to a point where there is very little virus circulating," Adams said. "The good news is that their illness should be very mild."

The vaccines are meant to prevent hospitalisations and deaths

Out of more than 95 million fully vaccinated Americans, less than 0.01% of them got breakthrough infections, the CDC reported at the end of April. That includes at least 594 hospitalisations and 112 deaths related to Covid-19.

Around half - 45% - of breakthrough infections occurred in people aged 60 and older. That includes cases in nursinghomes, where residents and staff were among the first Americans to get vaccinated. Elderly people with preexisting conditions may be prone to more severe illness, and transmission is more likely to occur in congregate living settings.

Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia, told Insider that even with a smattering of breakthrough infections taken into account, the vaccines have met the goal of protecting most people from severe illness.

"The goal of these vaccines is to keep you out of the hospital and keep you out of the ICU and keep you from dying," Offit said. "If you have a mild infection where you're PCR positive and have essentially an asymptomatic infection, that's fine."

Breakthrough cases may cause some symptoms, but they're usually mild

Some breakthrough infections are so mild they may as well be asymptomatic. Camme, for instance, was not sick enough to suspect she had Covid-19 at first.

Masha Gessen, 54, a staff writer for the New Yorker, also got sick despite being fully vaccinated. Her illness was fairly mild, she wrote for the magazine - her symptoms included a runny nose, itchy eyes, fatigue, and loss of smell.

Gessen recovered in about a week, which seems to be the case for most people with mild breakthrough infections.

An article in the New England Journal of Medicine described two similar cases that both resolved within a week or less after testing positive: a 51-year-old woman who had a sore throat, congestion, headache, and loss of smell; and a 65-year-old woman who was also congested, fatigued, and headachy.

The worst of Camme's symptoms started a week after she tested positive. She noticed she felt winded walking from her car to work, stopping to catch her breath. She's also been nauseous and has had migraines, chills, and night sweats for nearly a month since her positive Covid test.

Breakthrough infections may be less contagious to others

Even though Camme is still experiencing some symptoms due to her breakthrough infection, she sees a silver lining in the fact that she didn't pass the virus on to her loved ones.

"My partner didn't even get the vaccine and he didn't get the virus, and we were sleeping in the same bed until I tested positive," Camme said. "That's the thing - you may still get it, but the chance of you having to feel guilty about spreading it is a little bit less."

People who get Covid-19 despite being fully vaccinated typically have much less virus in their systems, meaning that they may be less contagious to others, Israeli studies have found. The articles have yet to be peer-reviewed, but the findings are promising.

More studies from Israel have also shown that the Pfizer vaccine may be 94% effective at preventing asymptomatic infections, which reduces the risk of someone unknowingly transmitting the virus.

Vaccinating the majority of people is key to stopping infections

To entirely eliminate the risk of getting Covid-19, more people need to get vaccinated, Offit said. He estimated that 80% of the population needs to be immunised - either through vaccinations or natural infections - to get the US out of the woods.

"This virus is going to be with us for a while," Offit said. "But the goal is to control spread, which I think we're gradually doing."

Even after her breakthrough infection, Camme maintains a positive attitude and faith in the vaccine.

"I'm an advocate for the vaccine," she said. "The only way that we're going to get through this is if everybody or majority of the population gets vaccinated. I think that's the only step forward that we can take to being a more normal world again."

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