COVID-19 vaccination adverse events rare in cancer patients

A territory-wide cohort study of Hong Kong cancer patients finds a low incidence of adverse events of specific interest (AESI) following vaccination with two doses of either BNT162b2 or CZ02.

“Currently, the safety of COVID-19 vaccines remains a concern, especially among the elderly and immunocompromised patients, including those with cancer, which has led to lower rates of vaccine uptake among cancer patients in Hong Kong,” wrote researchers from the University of Hong Kong (HKU). [Lancet Reg Health West Pac 2022;doi:10.1016/j.lanwpc.2022.100441; Vaccines (Basel) 2021;doi:10.3390/vaccines9070792] “Most patients with cancer were excluded from pivotal clinical trials of BNT162b2 and CZ02 vaccines as cancer treatments may suppress or impair the immune system. The available small observational studies of BNT162b2 and CZ02 in cancer patients have only assessed common adverse events, such as headache and fever, and did not provide suitable between-individual comparisons.” [Ann Oncol Off J Eur Soc Med Oncol 2021;32:569-571]

The current HKU study aimed to describe and assess the risk of WHO-defined AESI among patients with active cancer and a history of cancer who received vaccination with BNT162b2 or CZ02. Hospital Authority–managed electronic records of 74,878 patients (vaccinated, 25,789 patients; unvaccinated, 49,089 patients) were divided into an active cancer cohort and a history of cancer cohort. Within each cohort, patients who received two doses of BNT162b2 or CZ02 were matched 1:1 to unvaccinated patients using propensity score. [Hematol Oncol 2022;doi:10.1186/s13045-022-01265-9]

Among patients with active cancer, the 28-day incidence of AESI, which included acute respiratory distress syndrome, acute kidney injury, myocarditis, and thrombocytopenia, was 0.31 per 10,000 person-days for BNT162b2 recipients vs 1.02 per 10,000 person-days for unvaccinated patients. For CZ02 recipients, the incidence was 0.13 per 10,000 person-days vs 0.88 per 10,000 person-days for unvaccinated patients.

Among patients with history of cancer, the incidence was 0.55 per 10,000 person-days for BNT162b2 vs 0.89 per 10,000 person-days for those unvaccinated for COVID-19. Corresponding values were 0.42 per 10,000 person-days for CZ02 and 0.93 per 10,000 person-days for no vaccine.

“Neither vaccine was associated with a higher risk of AESI for patients with active cancer [BNT162b2: hazard ratio (HR), 0.30; 95 percent confidence interval (CI), 0.08–1.09; CZ02: HR, 0.14; 95 percent CI, 0.02–1.18] or patients with history of cancer [BNT162b2: HR, 0.62; 95 percent CI, 0.30–1.28; CZ02: HR, 0.45; 95 percent CI, 0.21–1.00],” highlighted the researchers.

In the active cancer cohort, there were two deaths in the BNT162b2 group vs 22 deaths among matched unvaccinated patients, and no deaths in the CZ02 group vs 12 deaths among matched unvaccinated patients. Among patients with history of cancer, one death occurred in the BNT162b2 group vs 13 deaths among matched unvaccinated patients, and two deaths in the CZ02 group vs 17 deaths among matched unvaccinated patients.

“The low rate of COVID-19 vaccine uptake in our study appears to reflect safety concerns among patients with cancer in Hong Kong. On 30 September 2021, our data showed that the overall vaccination rate in Hong Kong was 58.8 percent, while it was only 30.2 percent among patients with cancer. Our study provides reassurance that patients with cancer are not at increased risk of AESI or death following two doses of either BNT162b2 or CZ02,” concluded the researchers.