Pfizer-BioNTech’s COVID-19 vaccine effective and safe for use among cancer patients

By Sally Robertson, B.Sc.Jul 11 2021

Researchers in Israel have conducted a study showing that the use of Pfizer-BioNTech’s coronavirus disease 2019 (COVID-19) vaccine appears to be safe and effective among patients with cancer.

“To our knowledge, this study is the first to prospectively characterize the serologic status, immunogenicity, and safety of the BNT162b2 vaccine in a cohort of patients with solid tumors who are receiving active anticancer therapies,” writes the team from the Rambam Health Care Campus, the Rappaport Faculty of Medicine, and the Technion-Integrated Cancer Center, in Haifa.

While the efficacy and safety profiles of COVID-19 vaccines have previously been demonstrated in phase 3 studies, the team says patients with cancer were not adequately represented in these trials.

“Owing to the recommendation to prioritize high-risk populations for vaccination, further data are warranted,” says Irit Ben-Aharon and colleagues.

As reported in JAMA Oncology, the team’s prospective cohort study of more than 230 cancer patients found that administration of Pfizer-BioNTech’s BNT162b2 vaccine appeared to be safe and achieved satisfactory levels of antibodies (seropositivity) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the causative agent of COVID-19.

Study: Serologic Status and Toxic Effects of the SARS-CoV-2 BNT162b2 Vaccine in Patients Undergoing Treatment for Cancer. Image Credit: hedgehog94 / Shutterstock

Although there was a pronounced lag in antibody production among the cancer group, compared with among healthy controls, seroconversion occurred in most cancer patients following the second dose and any adverse events reported resembled those reported among healthy individuals.

Cancer patients may be at risk of more severe COVID-19

Some studies have shown that patients with cancer may be at risk for more severe COVID-19, with metastatic cancer, hematologic malignant neoplasms, and lung cancer reported as the major risk factors.

However, other studies have reported no such additional risk among cancer patients, compared with the general population.

Regulatory agencies approved the BNT162b2 vaccine developed by Pfizer-BioNTech based on a phase 2/3 trial of more than 43,500 participants who received two doses of the vaccine separated by a 21-day interval.

However, “although cancer had not been an exclusion criterion in the trials, the use of cytotoxic therapy or systemic corticosteroids throughout the study were considered as such in the pioneer study,” says Ben-Aharon and colleagues.

Mass immunization with BNT162b2 began in Israel in January 2021

In December 2020, the vaccine was approved for use in Israel and a mass immunization program was initiated on January 10^th, 2021. Healthcare workers and high-risk populations, including patients with cancer, were prioritized as the first in line for vaccination.

“Although real-world data regarding vaccine effectiveness are emerging depicting a positive outcome in the general population, there is a paucity of data regarding the efficacy and safety in the population of patients with cancer,” say the researchers.

Despite this lack of data, several professional organizations have recommended vaccination of patients with cancer, with guidelines encompassing all cancer patient populations, irrespective of treatment type, adds the team.

What did the researchers do?

As mass vaccination of high-risk populations was launched in Israel from January 10^th, 2021, the researchers enrolled and followed up vaccinated cancer patients during their routine visits to the Division of Oncology of Rambam Health Care Campus between January 15^th and March 14^th, 2021.

The study cohort included 232 patients with solid tumors who were receiving active treatment following a first or second dose of the BNT162b2 vaccine and 261 age-matched healthcare workers who served as controls.

Serum samples were collected after each vaccine dose and questionnaires were administered regarding sociodemographic factors and adverse reactions.

A regulatory agency-approved assay was used to assess anti-SARS-CoV-2 immunoglobulin G (IgG) antibodies in samples collected before the second dose (more than 10 days after the first dose) and in samples collected 14 days after the second dose.

What did the study find?

Of the 232 patients receiving cancer treatment, 132 were men (57%) and the mean age was 66 years (age range 25 to 88).

Of the 261 control participants, 118 were men (45%) and the mean age was 59 years (age range 25 to 81).

Most of the patients (74%) had metastatic disease and the most common cancers were gastrointestinal (27%), genitourinary (21%), lung (19%), and breast (18%).

The treatment protocols being followed were chemotherapy among 58%, biological agents (35%), and immunotherapy (36%), with some patients receiving more than one treatment type.

After the first vaccine dose, 29% of the cancer patients were seropositive, compared with 84% of the controls.

However, seroconversion occurred at higher rates in the cancer cohort following the second dose, with the seropositivity rate reaching 86%.

The adverse events reported by cancer patients were similar to those previously reported by healthy individuals.

What did the authors conclude?

The team says that the BNT162b2 vaccine appears to be safe, with satisfactory levels of seropositivity in patients undergoing treatment for cancer, although protection may occur later, compared with healthy individuals.

The researchers also say the results imply that a potential intention to decline a second vaccine by some jurisdictions owing to a shortage of vaccines warrants reevaluation of unique populations, such as patients with cancer, in view of lagging immunogenicity.