SAN DIEGO (KGTV) -- Starting next month, California will offer COVID-19 vaccines to people with high-risk underlying conditions like cancer.
A lot of cancer patients have questions. Should you delay the vaccine if you’re undergoing chemotherapy? What happens if you get the vaccine while your immune system is shot?
The Centers for Disease Control and Prevention offers limited guidance. Vaccine makers excluded people with compromised immune systems from their trials.
For the roughly 17 million Americans who previously had cancer and beat it, the advice is simple: get the shot when it is offered to you.
But experts say the recommendations are more nuanced for patients with active cancer who are undergoing treatments.
For patients undergoing treatments that impact the immune system like chemotherapy, the timing of the vaccine is important to maximize its protective benefits, according to Dr. Thomas Buchholz, the medical director of Scripps MD Anderson Cancer Center.
One thing is clear: cancer and COVID-19 are a dangerous combination. For every four cancer patients who contract the virus, one will die, according to research published in September that analyzed dozens of studies.
The scientists found cancer patients had a stunning death rate of 25.6 percent (that number is “unadjusted,” meaning some of the individuals may have had additional risk factors like age). Typically, 2 to 3 percent of the people who contract COVID-19 die from it, depending on the country.
It’s not yet clear if this higher risk from COVID-19 extends to people who had cancer in the past and beat it.
Doctors are confident the currently authorized mRNA vaccines are safe for patients whose immune systems are compromised by treatments like chemotherapy.
The concern is that vaccination in these individuals might produce fewer protective antibodies and T cells to fight COVID-19, Dr. Buchholz said.
"It really has to do with how effective the vaccines will be. Are they going to be as effective as in patients who aren't receiving chemotherapy?" he said.
The reason? Chemotherapy attacks rapidly dividing cells. That includes cancerous cells and the white blood cells that the vaccines are trying to jumpstart. White blood cells include T cells, which coordinate the immune response, and B cells, which produce those precious antibodies.
When you’re on chemo, there are fewer white blood cells available for the vaccine to train.
“The good news is these white blood cell counts recover, and they recover quite quickly,” said Dr. Buchholz.
Waiting one or two weeks after a round of chemotherapy might be all a patient needs to maximize their immune response, he said.
“Our recommendation is to carefully follow the white blood cell count, and perhaps give vaccination during the course of chemotherapy at a time when our white blood cell counts have recovered from a particular course,” he said. “And so we could introduce it in the cycles of chemotherapy.”
Other specialized treatments might warrant a longer delay before vaccination, like engineered CAR T-cell therapy or a bone marrow transplant. In those cases, a doctor might encourage the patient to wait three months before getting the shot, Dr. Buchholz said.
Radiation does not typically affect the immune system, he said, so those patients should be good to go to get the shot.
An article published this month in the journal Lancet says cancer patients will likely need repeat vaccinations or booster shots during their lifetime to maintain protection against the virus. But the CDC says at this time, re-vaccination is not recommended.
However, the agency notes that advice “may be updated.”