Immunogenicity and safety of a two-dose live attenuated varicella vaccine given to adults following autologous hematopoietic stem cell transplantation.

BACKGROUND

Immunogenicity and safety of varicella vaccine (Varilrix(™) [Oka-RIT]; GlaxoSmithKline Vaccines) in adults who had undergone autologous hematopoietic stem cell transplantation (HSCT) were assessed (September 2003 to September 2007; NCT00792623).

METHODS

Two Oka-RIT doses were given at 4.5 and 6.5 months post transplantation. Humoral immune responses were assessed using an immunofluorescence assay (anti-varicella zoster virus [VZV] antibody; cutoff 1:4) after each vaccine dose. Solicited local (8 day) and general (43 day), unsolicited (until day 43) adverse events (AEs) after each vaccine dose and serious adverse events (SAEs) (until 17.5 months post dose 2) were recorded.

RESULTS

Of 45 patients, 19 were included in the according to protocol cohort for immunogenicity; 15 patients had pre- and post-vaccination serum samples positive for anti-VZV antibodies. Vaccine responses (anti-VZV antibody titer ≥1:4 in seronegative patients, and ≥4-fold increase in anti-VZV antibody titer in seropositive patients) were elicited by only 2 patients 2 months post dose 1, and by a single patient 1.5 months post dose 2. Although no major safety signals were detected, any and Grade 3 solicited AEs that were causally related to vaccination were reported by 44.8% and 10.3% patients, respectively. During the 43-day follow-up period, 3 patients developed varicella-like rash (1 vaccine-type VZV). Beyond 43 days, herpes zoster was reported in 2 patients and wild-type varicella infection in 2 patients (1 was breakthrough infection). Four non-fatal SAEs were reported by patients and considered causally unrelated to vaccination.

CONCLUSION

Oka-RIT was poorly immunogenic but safe when given to adults up to 6 months post autologous HSCT, and alternative strategies are required to prevent VZV-associated complications in these populations.