p.i., but none of the animals showed rise in body temperature (data not shown). At both 3 and 14 d.p.i. there was no virus replication in the brains, spleen and intestine (data not shown). This study confirmed the attenuated phenotype of a A/17/California/2009/38 pandemic LAIV candidate in a ferret model. The results of immunogenicity study showed that a single dose of pandemic LAIV was sufficient to induce adequate immune responses against the wild type strain. Moreover, vaccinated animals

proved to be protected against challenge with a virulent wild type pandemic H1N1 virus (Table 2). The monovalent LAIV contained 7.0 log EID50 Baf-A1 nmr per 0.5 ml dose for adults and 6.5 log EID50 for children. Following successful preclinical studies, a Phase I/II randomized, controlled, double-blind clinical study was carried out in 120 adults aged 18–60 years randomly divided into groups to receive

either the vaccine (100) or the placebo (20) administered intranasally in two doses given at 21 days apart. Standard haemagglutinin inhibition (HAI) assays were performed and influenza virus-specific serum IgG and IgA antibodies in nasal swabs were tested by enzyme-linked immunosorbent assays (ELISA) using whole purified virus at 16 HAU per 0.05 ml for absorption. No clinically significant solicited adverse events attributable to the LAIV RAD001 were detected seven days after vaccination (Table 3). The few reactions reported were of short duration and without sequelae. HAI and ELISA tests were also used to determine the serological

response in 66 adult subjects (Table 4). Although post-vaccination serum HA antibody titres were low, cumulative data from both assays resulted in 42.5% and 70.2% conversion after the first and second inoculation, respectively. Peripheral blood mononuclear cells were obtained for analysis by cytokine tests at various times following the first and second vaccination from a limited number of volunteers (16 vaccinees and 9 placebo recipients, respectively). Fig. 1 represents post-vaccination Cell press changes (n-fold) of cellular immune response mediated with virus-specific CD3+CD4+IFNγ+ and CD3+CD8+IFNγ+ memory T cells in volunteers who received LAIV and placebo. After revaccination, the mean increases of both CD4+ and CD8+ memory cells were significantly higher in vaccinated volunteers compared with the placebo group. Interestingly, the same effect of vaccination was also observed in vaccinees without reliable conversions of HAI antibody titres. Even after a single vaccination, the rate of volunteers with a significant increase of these cells in the blood (i.e. results exceeding 2 standard deviations of placebo mean value) was 37.5% (CD8+) and 75.0% (CD4+). After revaccination, the percentage of individuals with significant rises in CD8+ and in CD4+ cells was 68.8%. HAI test results in children were much higher, i.e. 41.4% and 83.