July 8 (UPI) -- The two-dose Pfizer-BioNTech COVID-19 vaccine provides an effective immune response and is safe in people undergoing treatment for certain types of cancer, a study published Thursday by JAMA Oncology found.
Compared to those without the disease, however, people with cancers caused by solid tumors, such as breast, colon and lung cancers, may have a "lagging" immune response to the vaccine, the researchers said.
The study did not assess the effects of the Moderna two-dose COVID-19, which has a similar composition, on patients receiving treatment for cancer, so it is unclear whether it would produce the same response, though earlier studies suggest it does.
"Cancer patients with solid tumors do develop antibodies to the vaccine, but this process is lagging compared with the general population, and one dose is not enough," study co-author Dr. Irit Ben-Aharon told UPI in an email.
"The vaccine appears safe and effective since throughout the study period there were no significant cases of COVID-19 infection in the study population," said Ben-Aharon, an associate professor of oncology at the Rambam Health Care Campus in Haifa, Israel.
Still, the Pfizer-BioNTech vaccine may cause potentially concerning changes in certain liver enzymes in people undergoing chemotherapy and radiation, according to Ben Aharon.
As a result, vaccinated patients should be monitored for these changes as part of their routine care, he and his colleagues said.
The two-dose vaccines from Pfizer-BioNTech and Moderna both use modified genetic material from the coronavirus to stimulate the immune system to create antibodies against it.
These antibodies, or cells created by the immune system to fight off viruses, are present in the blood after one dose of the vaccines, but offer more complete protection following the second, research suggests.
Both two-dose vaccines are approved for use in the United States and clinical trial results indicate they offer up to 95% protection from severe COVID-19 in those fully vaccinated.
However, clinical trials of the vaccines to date have not included sufficient numbers of participants with cancer or those undergoing treatment for the disease to gauge their efficacy in this population, according to Ben-Aharon and his colleagues.
For this study, the Israeli researchers compared antibody responses after vaccination in 232 adults receiving chemotherapy or radiation treatment for cancer with those of 220 healthy adults.
All of the study participants received the Pfizer-BioNTech vaccine the researchers said.
After their first dose, 29% of the cancer patients had detectable antibodies in their blood, compared with 84% of those without the disease, the data showed.
The antibody response among the participants with cancer improved following the second dose, when 86% had detectable levels in their blood, said the researchers, who are monitoring the cancer patients for six months to determine if their immune response declines and a booster dose is needed.
Based on their findings, however, people undergoing cancer treatment can -- and should -- receive both doses of the vaccine, Ben-Aharon said.