COVID-19 vaccines appear effective in patients with thoracic cancer, and a third shot is beneficial in those with low antibody titers, according to a study published in the Journal of Thoracic Oncology.

This prospective study included 306 patients with thoracic cancer who received the Pfizer-BioNTech COVID-19 vaccine (n=302), the Moderna vaccine (n=1), or the AstraZeneca vaccine (n=3).

The patients had a median age of 67 years (range, 27-92 years), and 59.2% were men. Most patients (84.9%) had non-small cell lung cancer. Nineteen patients (6.2%) had a history of SARS-CoV-2 infection.

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The study’s primary objective was to assess humoral responses to vaccination. The median follow-up was 6.7 months.

There were 283 patients (92.5%) who had serological testing at day 28 after the first vaccination and received a second vaccine dose that day. Serological data were available for 269 (88%) patients at day 42, which was 2 to 9 weeks after their second vaccination.

Among patients who did not have a previous SARS-CoV-2 infection or had anti-N negative immunoglobulin G (IgG) at day 0 and day 28, 248 samples were available at day 42 (at least 14 days after the second dose). The median serum anti-S IgG titer was 4725 AU/mL (interquartile range, 1066-13,698 AU/mL).

There was an overall increase in serum anti-S IgG titers 2 to 9 weeks after the second vaccine dose, with a mean 1.4- to 2-fold increase in log10 anti-spike IgG concentrations. However, 17 patients (6.3%) still had negative serological testing, and 34 (11%) had IgG concentrations of 300 AU/mL or lower.

At day 42, 30 patients with anti-S IgG titers at 300 AU/mL or below were offered a third vaccination. There were 26 patients evaluable at day 28 after the third dose, and 88.5% of them experienced seroconversion. There were 3 patients who did not respond to the third vaccination. Two were totally negative, and 1 had low anti-spike antibodies.

There were 8 patients (2.6%) who had PCR-proven SARS-CoV-2 infection during the follow-up. None of these patients had received a third vaccine dose. Infections were considered mild, with 1 patient being hospitalized due to frailty. 

There were no allergic reactions to the vaccines and no significant safety concerns in the 278 patients for whom safety data were available.

The researchers noted that, to their knowledge, this is the largest series of thoracic cancer patients receiving COVID-19 mRNA vaccines published to date. Still, the sample size of the different patient subsets was limited. 

Furthermore, due to the observational study design, the researchers did not perform systematic recurrent rhino-pharyngeal swabs for SARS-CoV-2 and may have missed asymptomatic infections.

Nevertheless, the researchers concluded that a third vaccine dose could contribute to appropriate sero-protection in patients still poorly immunized after 2 doses. 

“Patients with lymphocyte function defects due to lymphoid cancers or lymphocyte-depleting treatments may exhibit lower benefits from a third vaccination,” the researchers wrote.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Gounant V, Ferré VM, Soussi G, et al. Efficacy of Severe Acute Respiratory Syndrome Coronavirus-2 vaccine in patients with thoracic cancer: A prospective study supporting a third dose in patients with minimal serologic response after two vaccine doses. J Thorac Oncol. Published online November 16, 2021. doi:

This article originally appeared on Cancer Therapy Advisor