COVID-19 vaccines remain highly protective against severe disease and death in most people, but their effectiveness against infection wanes significantly over several months.  

A breakthrough case is when a vaccinated person gets infected with the virus they were vaccinated against. When more people get vaccinated, there are more people in the pool who can get a breakthrough infection. As vaccination rates go up, breakthrough infections may also go up.

According to the Oregon Health Authority’s latest breakthrough case report, there have been 47,687 breakthrough cases in Oregon. This is a very small proportion (less than 2 percent) of the 2.7 million Oregonians who have been fully vaccinated.

Do breakthrough cases mean the vaccines aren’t working?

No. The vaccines continue to protect people against infection, hospitalization and death. Most COVID-19 cases are still occurring in unvaccinated people. For example, for the week of Nov. 28 through Dec. 4, there were approximately 3-1/2 times as many cases among unvaccinated people as there were among those who are fully vaccinated. People who do get a breakthrough infection are also much less likely to experience severe disease than unvaccinated people.

Are some people more likely to get COVID-19 even after they’re vaccinated?

Some people are at higher risk. OHA’s latest breakthrough case report shows that in Oregon, almost 80% of vaccine breakthrough deaths have occurred in people 70 years and older. This may be due to increased disease severity caused by the Delta variant and waning vaccine immunity over time in elderly populations, since they were among the first groups to get the vaccine. This is another good reason to get a booster dose.

Living in an area with high COVID-19 transmission may be another reason. If you’re around more people who are infected, your risk is greater. This is why wearing a mask indoors is still a good idea for everyone – vaccinated or not.

People who are immunocompromised may also be at greater risk of breakthrough infections. Medical experts recommend immunocompromised people get three primary doses of mRNA vaccine (Pfizer or Moderna) and one booster dose, or one dose of Johnson & Johnson and one booster dose.

Booster doses help people maintain strong immunity to disease longer

The first vaccine series builds up the immune system to make the antibodies needed to fight the disease. Over time, the immune response weakens. A booster dose builds on the initial response and tends to result in higher antibody levels that help people maintain their immunity longer. Everyone age 18 and older is eligible to receive a booster dose.

What can we do to protect against breakthrough infections?

After nearly two years of pandemic life, we know how to stay safe:

• Get a third dose if you are immunocompromised and a booster dose if you’re eligible.
• Wear a well-fitting mask (ages two and up) when indoors with persons outside your household.
• Avoid large indoor gatherings.
• Wash hands regularly.