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Breakthrough COVID-19 cases expected to become more common in coming months

Ariel Cohen, CQ-Roll Call on

Published in News & Features

WASHINGTON — Mild cases of COVID-19 among vaccinated individuals are becoming increasingly common as the highly contagious delta variant barrels through communities, but physicians and public health experts say that shouldn’t be a cause for significant concern.

A breakthrough case of COVID-19 occurs when a person contracts COVID-19 at least two full weeks after the final dose of the vaccine. The Centers for Disease Control and Prevention tracks only breakthrough cases that result in hospitalization or death, as these incidences are both serious and very rare.

COVID-19 cases are up to five times more common in unvaccinated individuals compared with the vaccinated, according to the CDC. But state-level data shows that milder breakthrough cases that do not result in hospitalization are on the rise among the fully vaccinated as virus transmission increases and vaccine efficacy decreases. And they’re expected to keep increasing.

“It’s likely that everybody will probably get infected with COVID-19 [at some point] because it’s an endemic respiratory virus. The goal is to make sure that at that time, that infection occurs after you’ve been vaccinated so it’s mild,” said Amesh Adalja, a doctor and infectious disease specialist at Johns Hopkins Center for Health Security.

A mild breakthrough infection counts as any case of COVID-19 in a fully vaccinated person that does not require hospitalization. Fortunately, these are the vast majority of breakthrough cases, and for some, they are asymptomatic.

But for many otherwise healthy individuals, these so-called mild cases do not feel mild at all.


Fevers, muscle aches, congestion and extreme fatigue are common symptoms of a breakthrough infection, similar to a bad case of the flu. It’s not unusual for a person with a breakthrough infection to feel lingering symptoms for several weeks, but physicians say the worst ailments, such as a hacking cough or searing headaches, usually let up in two weeks or less.

Mild breakthrough cases also require sick individuals to quarantine and stay home from work or school, regardless of their symptoms. Their family members and other close contacts may also have to isolate and monitor symptoms.

The early symptoms of a COVID-19 breakthrough case can often be mistaken for a cold or allergies, leading an infected but unaware individual to potentially spread the coronavirus to others.

Levels of community spread play a key role in how common and how severe breakthrough infections are.


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