Originally published by the Washington State Department of Health.

Chances are, you’ve recently heard some talk about breakthrough COVID-19 cases.

The delta variant is currently spreading through the US at an incredible rate. While it’s most contagious (and dangerous) among unvaccinated people, there are still a few fully vaccinated people testing positive for COVID-19.

We understand how discouraging this may sound, especially since a post-pandemic world felt so close a few weeks ago. Although this may be disappointing, it’s not necessarily unexpected. In fact, there are still reasons to feel encouraged.

What is a breakthrough case?

A breakthrough case happens when someone who is fully vaccinated (14 days past their final vaccine dose) tests positive for the virus. People who catch COVID-19 within these 14 days are not classified as breakthrough cases since their body had not built full protection yet.

Is this normal?

Yes, breakthrough cases should be expected. That’s because none of the COVID-19 vaccines are 100% effective at preventing infection. There are different reasons why, but it’s largely because viruses evolve over time and undergo changes as they spread and replicate. This is also common for non-COVID vaccines, and it’s why we need flu shots every year.

So, in part, it simply comes down to numbers. Billions of people are vaccinated. With numbers that large, even if the vaccine is working as expected, some people will still become infected with COVID-19.

I’m fully vaccinated… should I be worried?

Fully vaccinated people have much stronger protection against COVID-19 compared to those who aren’t. Vaccinated people who get infected are less likely to experience symptoms (if any), compared to those who are unvaccinated. Vaccinated people are also likely to recover faster, even against delta.

CDC data shows that over 99.99% of people who were fully vaccinated against COVID-19 did not die or even require hospitalization. The highest hospitalization rates remain in areas with low vaccination rates.

That said, some vaccinated people can still get delta variant breakthrough infections and spread the virus to others. Previous variants produced less viral loads in fully vaccinated people than in unvaccinated people. In contrast, the delta variant seems to produce the same high amount of viral load in both unvaccinated and fully vaccinated people.

So, keep your guard up, especially if you’re often around people who aren’t eligible for the vaccine (like young children). Wear a mask in public settings, practice physical distancing, wash your hands often, and enable WA Notify on your smart phone.

How common are breakthrough cases?

Breakthrough cases are still considered to be very rare. They appear to be most common among new variant strains. It’s hard to get an exact count since many vaccinated people don’t show symptoms, and therefore, don’t get tested.

Washington state data shows there were 21,757 vaccine breakthrough cases among more than 4.1 million vaccinated people from Jan. 17 — Aug. 21, 2021. Although that might sound like a high number, it means that only 0.5% of vaccinated Washingtonians had breakthrough infections. Of the breakthrough cases that we have data for, just 9% required hospitalization and less than 1% died of a COVID-related illness.

Should I get a different vaccine or a booster for extra protection?

Vaccine breakthrough has been associated with all three current authorized vaccines. Vaccines require different dosing schedules and build resistance at different rates, so some achieve full vaccination more quickly than others. And, since we administered more of some brands than others, it’s extremely difficult to compare numbers of breakthrough cases among vaccine brands.

The good news is that all the COVID-19 authorized vaccines are found to be safe and effective in preventing severe illness, hospitalization, and death.

Health care providers may now offer third doses of Pfizer-BioNTech and Moderna COVID-19 vaccines to certain immunocompromised individuals. This follows recommendations from the U.S. Food and Drug Administration (FDA), Advisory Committee on Immunizations Practices (ACIP) and Western States Scientific Safety Review Workgroup.

Right now, boosters are not recommended for the general public, but we expect more guidance on this soon. Check back in the coming weeks for a blog post with more information.