Zoster vaccine response held up during cyclophosphamide

Design

Subanalysis of a prospective randomised placebo-controlled vaccine trial

Population

41 patients on IV cyclophosphamide, 164 rheumatic disease patients without it, 164 healthy controls

Primary outcome

Humoral seroconversion after two doses

Effect

91.9% with cyclophosphamide vs 91.5% without vs 99.4% in controls

Intravenous cyclophosphamide is widely assumed to blunt vaccine responses, so many clinicians defer vaccination until a course ends. This subanalysis of a randomised, placebo-controlled trial of the recombinant zoster vaccine compared 41 patients with autoimmune rheumatic disease receiving intravenous cyclophosphamide, 164 patients with rheumatic disease not receiving it, and 164 healthy controls. All had two doses.

Seroconversion was 91.9% with cyclophosphamide and 91.5% without, both lower than 99.4% in controls. Antibody titres and cellular responses were similar in the two rheumatic disease groups. Disease flares did not differ and there were no serious adverse events.

The cyclophosphamide group is small and the outcome is immune response, not prevention of shingles. But the result runs against the expectation of a very poor response.

Patients on cyclophosphamide, often with lupus nephritis or vasculitis, are at high risk of shingles. These data support giving the recombinant vaccine during treatment rather than waiting. Availability and cost in India remain a constraint.

• Consider giving the recombinant zoster vaccine during a cyclophosphamide course rather than deferring it
• Use the two-dose recombinant vaccine, not the live vaccine, in immunosuppressed patients
• Vaccination did not trigger more disease flares in this study
• Review vaccination status at the start of any induction immunosuppression

Why it matters

It removes a common reason for postponing vaccination in the highest-risk patients.

Don't overread it

The study measured immune response, not shingles prevention, in a small cyclophosphamide group.

The statistics, in plain English

91.9% versus 91.5% is essentially identical. With only 41 patients on cyclophosphamide, a modest difference could still be missed, and antibody response is a surrogate for protection.

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