The COVID-19 vaccines currently available in the U.S. require two doses to reach their maximum efficacy of about 95%.
For the Pfizer-BioNTech vaccine, it's recommended that people receive the second dose within three weeks. For the Moderna vaccine, it's four weeks.
The number of doses available is currently limited, and there have already been delays with vaccine distribution in states across the country, including Oregon.
This has led to concerns from our viewers about what happens if a booster shot isn't administered within the recommended intervals.
So KGW's VERIFY team to find out: What happens if you don't get the second dose of the COVID-19 vaccine within three or four weeks?
The good news, according to state health officials, it's okay to get the second dose later than three or four weeks after the first dose.
People should get the second shot as close to the recommended interval as possible, said Oregon Health Authority (OHA) spokesman Timothy Heider.
"However, there is no maximum interval between the first and second doses for either vaccine," he said, adding that experience with other vaccines have shown a booster shot can be "quite effective" even if a vaccine series is delayed or interrupted.
Heider was unable to say how much delaying the second dose could reduce the COVID-19 vaccine's efficacy, but he said most vaccine booster doses can be given without restarting the vaccine series if given within a year, citing the World Health Organization.
The current recommendation is that anyone who misses the three-week or four-week mark for the second dose should try to get it "as soon as possible," he said. The second dose should not be administered any earlier than the recommended interval.
Heider said people should get the second dose even if they had side effects from the first, unless a vaccine provider or your doctor says they shouldn't.
"Remember that it takes time for your body to build protection after any vaccination," said Heider. "COVID-19 vaccines that require two shots may not protect you until a week or two after your second shot."
And as for getting just one dose and skipping the booster altogether?
OHA doesn't have specific data on vaccine efficacy from a single dose, but "experience from other vaccines suggest that an incomplete series may lead to decreased vaccine efficacy and shortened immune memory," said Heider.
Do you have something you want us to VERIFY? Let us know. Email us at VERIFY@kgw.com.