Vaccination of cancer patients with whole-virion, adjuvant-free pandemic influenza H1N1 vaccine: Patient acceptance and vaccine immunogenicity.

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e16574 Background: During the H1N1 pandemic 2009, a whole virion, verocell derived, inactivated, unadjuvanted influenza vaccine (A/California/07/2009 (H1N1)v) was used in Austria. This was the only adjuvant-free pandemic H1N1 vaccine licensed in Europe at this time. The objective of this study was to evaluate cancer patients’ acceptance of the vaccine and its immunogenicity. Methods: Adult patients with malignant diseases and concurrent chemotherapy were recruited during the pandemic, which was widely publicised in the media from Nov. 2009 to March 2010. Patients were offered free vaccination on the day of their chemotherapy. The vaccination schedule consisted of two intramuscular injections in an at least 3 week-interval. Efficacy of the vaccination was assessed by using a haemagglutination inhibition (HI) assay before and after each vaccination. The primary immunological end point was seroconversion rate which was defined as the proportion of subjects with a 4-fold increase in HI titer. H1N1 specific IgG was determined by ELISA. Results: 260 (91%) out of a total of 286 cancer patients refused to be vaccinated, whereas the remaining 26 patients (9%; n=15 females, n=11 males) agreed. The patients’ median age was 62 years. The studied patients had cancers of the breast (n=14), bladder (n=3), prostate (n=3), colon (n=2), pancreas (n=2), breast/colon (n=1) and prostate/liver (n=1). In 20 patients, the fully scheduled course of 2 vaccinations took place. Before the first vaccination, 54% (n=13) of the patients had HI titer >1:40 and only one was positive for virus-specific IgG. After 1st vaccination, 13% (n=3) had experienced seroconversion in the HI, whereas 38% were seropositive for IgG. After 2nd vaccination, 33% (n=4) had seroconversion in the HI, whereas 50% were seropositive for IgG. Seroconversion occurred in 60% of patients <60 years and in 12% of patients > 60 years. In contrast, the development of virus-specific IgG was seen in 80% and 38% of patients. Conclusions: Our results have demonstrated a very low acceptance of the pandemic H1N1-Influenza vaccine in cancer patients. The licensed adjuvant-free vaccine resulted in only limited protective immune responses.

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