Pfizer-BioNTech Booster Vaccine Significantly Improves Immune Responses in Patients With Cancer

Patients from the United Kingdom (U.K.) who had an active diagnosis of cancer experienced significantly improved immune responses to the Pfizer-BioNTech COVID-19 vaccine after receiving the booster shot 21 days after the first dose, according to data from a recently published observational study.

The results, according to the study authors, indicate the importance of prioritizing patients with cancer for receipt of an early second dose of the vaccine.

“In patients with cancer, one dose of the Pfizer-BioNTech vaccine yields poor efficacy,” they wrote. “Immunogenicity increased significantly in patients with solid cancer within two weeks of a vaccine boost at day 21 after the first dose.”

Of note, the U.K. government in 2020 announced that the general population should receive the second doses of the COVID-19 vaccine approximately 12 weeks after receiving the first dose. This recommendation is a departure from the three to four-week window suggested by the vaccine manufacturers — which the United States follows.

This data comes after the same group of researchers previously reported that after a SARS-CoV-2 infection, some patients with cancer (especially those with B-cell malignancies) showed a delayed or negligible development of antibodies, abnormally low activity in the immune system and prolonged virus shedding compared to those not diagnosed with cancer. Moreover, previous research has shown that older and immunocompromised patients — including those with cancer — experience minimal benefits from vaccines.

As a result, the authors sought to evaluate the effectiveness and safety profiles of vaccines against SARS-CoV-2 (the virus that causes COVID-19) in patients with cancer — specifically, with Pfizer-BioNTech.

A total of 134 patients with solid cancer and hematological cancer from three hospitals in the U.K. (Guy’s & St Thomas’ NHS Trust, King’s College Hospital and Princess Royal University Hospital) participated in the study. There were also 34 healthy individuals (controls) for comparison. Blood samples were collected before patients were vaccinated, and then three weeks after and five weeks after their first vaccination. A COVID-19 nasal swab test was also completed every 10 days or in cases of symptoms of COVID-19.

The 92 patients with solid cancer enrolled on the study received their anticancer treatments either within 15 days before (38 patients) or after (50 patients) their first dose COVID-19 vaccination.

By the end of the study, 736 blood samples had been processed to assess effectiveness of the Pfizer-BioNTech COVID-19 vaccine in patients with cancer, as well as virus neutralization and T-cell responses. The study authors noted that any samples obtained after March 19, 2021 are still being processed.

“The (Pfizer-BioNTech) vaccine was generally well tolerated in patients with cancer, even in those on immunotherapy who might have been anticipated to make exaggerated, inflammatory immune responses,” they wrote. “However, by three weeks following single-dose (30 microgram) vaccination, immunogenicity was low.”

Specifically, immunogenicity (the immune system’s response to the vaccine) was 38% in patients with solid cancer and 18% in those with hematological cancer and did not improve in the following two weeks. However, after receiving a booster shot on day 21, the response substantially improved in patients with solid cancer.

Almost all of the healthy controls (94%) in the study had antibodies (or considered responders to the vaccine) at approximately 21 days after the first vaccination, compared to 38% of patients with solid cancer and 18% of those with a hematologic cancer.

The authors noted that there were not enough patients with hematological cancer who received a booster shot to truly assess the impact of receiving the second dose on day 21 in those patients.

Fifty-four percent of the patients with cancer reported no side effects after receiving the first dose. After the second dose, no side effects were reported in 71% of patients with cancer. Compared with the healthy controls, 38% of which reported no side effects after the first dose and 31% after the second. The most reported side effect among patients with cancer (35%) and the healthy controls (48%) was pain at the injection site seven days following the first dose. There were no vaccine-related deaths.

The results of the trial were consistent with the low vaccine efficacy reported for patients with cancer receiving seasonal vaccines, the authors highlighted.

“(This trial implies) that single-dose (Pfizer-BioNTech) vaccination leaves most patients with cancer wholly or partially immunologically unprotected,” the authors concluded. “This finding is of particular concern given our and others’ observations that immunocompromised patients have a higher incidence of harboring persistent SARS-CoV-2 infections, possibly providing an important reservoir for the emergence of novel viral variants.”

The authors wrote that the data could be used to reassess the present U.K. policy of a 12-week Pfizer-BioNTech vaccine dosing interval in patients with cancer, as well as other high-risk groups. Additional studies that examine the immune system response after more, repeated boosting of immunocompromised patients are recommended. This population, specifically, should also continue to observe COVID-19-associated measures like physical distancing and masking, even after vaccination, according to the authors.

Before this data was published, the U.K. government noted in February the possibility of low vaccine responses in immunosuppressed patients and recommended those individuals schedule their second booster dose earlier than the 12-week window between doses.

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