Studies that looked at the efficacy of the COVID vaccines included tens of thousands of people each.
Those studies didn’t look into how well people with certain medical conditions might respond compared to the general population.
A paper, published in Jama Oncology, looked at both the efficacy and safety of the Pfizer vaccine in cancer patients who were receiving active treatment for their tumors. It touches on a related question: What is the vaccine effect in people with relative immune compromise?
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Cancer patients undergoing active treatment are often immune suppressed and that could mean the response to the COVID vaccine wouldn’t be as good as expected.
Researchers in Israel looked at 232 patients with cancer that were being actively treated and compared their antibody response after receiving the first and second dose of the Pfizer vaccine to 261 healthy, age-matched healthcare workers.
After the first vaccine dose, only 29% of the cancer patients responded and 84% of the healthy volunteers responded. After the second dose, 86% of the cancer patients responded. The lagging response emphasizes the importance of cancer patients receiving both doses.
The researchers also found that certain treatments and cancer types may have a greater effect on vaccine effectiveness. Twenty-nine percent of breast cancer patients did not develop antibodies after the second dose. Seventy-four percent of patients who didn’t respond to the vaccine were receiving chemotherapy. This would need more study before drawing any conclusions.
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From the standpoint of safety, the common pattern of side effects included pain at the injection site, fatigue, body aches, fever or other symptoms. It didn’t suggest any safety concerns.
Because the cancer patients in the study were receiving other routine tests as part of their treatment there were a couple of other things to note. About 10% of the patients had an increase in their live enzymes after their first dose and 5% of the patients had swelling of the neck or armpit lymph nodes after receiving the vaccine.
The study couldn’t say if a booster dose of the vaccine could improve the response. There is also still a question of the durability of the response in the group.
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