H1N1 Vaccine Effectiveness And Safety Reports

Wednesday, December 16, 2009

H1N1 Vaccine Effectiveness And Safety Reports

Posted by News Updates Today

H1N1 Vaccine Effectiveness And Safety Report That One Dose Is Needed For Adults And Two For Children.

December 17 2009 : Three studies from the USA , China , and Hungary shows that one dose of H1N1 influenza vaccine should give adults enough protection from infection. Two doses could be necessary for children aged less than 9 years in the USA study or less than 12 years for the Chinese study.

To find the correct antigen dose and injection schedule to protect against 2009 pandemic influenza A H1N1, information is wanted from large clinical trials in children, adults, and elderly people. The three studies report preliminary safety and immunogenic results after administration of pandemic H1N1 vaccines in these three countries.

Dr Martine Denis, Sanofi-Pasteur, Lyon , France , and colleagues reviewed the immune response generated by a vaccine approved by the US Food and Drug Administration. The manufacturer is Sanofi-Pasteur , PA , USA . This vaccine was produced in agreement with the process used to produce a regular seasonal influenza vaccine, as per World health organization (WHO) recommendations.

This preliminary report included two randomized controlled phase 2 trials. The participants were healthy children aged 6 to 35 months and 3 to 9 years and adults 18 to 64 years and 65 years and over. They were randomized to vaccine containing, per dose 7•5 μg (children and adults), 15 μg (children and adults), or 30 μg (adults only) haemagglutinin. Haemagglutinin is a protein on the flu virus surface used as an antigen to stimulate immune-reaction against the virus.

The research team evaluated 410 of 423 children and 724 of 750 who were given an active vaccine. 50 of 51 children and 95 of 99 adults were given placebo for immunogenicity on day 21. After active vaccination, between 45 percent (7•5 μg dose) and 50 percent (15 μg) infants aged 6 to 35 months were seroprotected.

The matching figures for the other age groups were 69 percent (7•5 μg) to 75 percent (15 μg) of 3 to 9-year-old children; 95 percent (7•5 μg) to 100 percent (30 μg) of 18 to 64-year-old adults; and 93 percent (15 μg) to 95 percent (30 μg) of elderly adults. There were no reports of vaccine-related serious adverse events. Injection-site and systemic reactions were reported by up to about 50 percent of every age and vaccine group. There were no noticeable differences between vaccine and placebo groups.

“One dose of vaccine was highly immunogenic in adults, telling that it afforded sufficient protection against this pandemic influenza A H1N1 virus. Two doses of vaccine will probably be needed in children younger than nine years. Safety and reactogenicity of the vaccine were acceptable and similar to those of seasonal vaccine. These preliminary results also show that a considerable proportion of children are already seroprotected after their first vaccination. We will report the immunogenic and safety of a two-dose vaccination schedule in children as soon as all the study results are available."

The randomized, placebo-controlled study recruited participants in ten centres in China . It included 12,691 people aged 3 years or older and assessed eight vaccine formulations.

The researchers found that seroprotection rates varied from 70 percent to 93 percent. This depended on the formulation used with the 30 μg non-adjuvant formula giving the best protection. An adjuvant is an agent that may stimulate the immune system and increase the response to a vaccine, without having any specific antigenic effect in itself.

As with the USA study, the 7.5 μg, non-adjuvant formula offered substantial seroprotection. It was 87 percent across all age groups protected compared to 10 percent for placebo. In terms of individual age groups, this 7.5 μg formulation induced seroprotection in 77 percent of children aged 3 to12 years; 97 percent of adolescents aged 12 to18 years; 90 percent of adults aged 18 to 60 years; and 80 percent of adults aged over 60 years. In children aged 3 to12 years, a second dose of this same 7.5 μg formulation increased seroprotection rates to 98 percent.

Most of the adverse reactions were mild or moderate, and self-limited. Severe adverse events occurred in 69 (0•6 percent) recipients of vaccine compared with one recipient (0•1 percent) of placebo. Fever was the most common severe adverse reaction. It occurred in 25 (0•22 percent) recipients of vaccine after the first dose and four (0•04 percent) recipients of vaccine after the second dose compared with no recipients of placebo after either dose.

"We recommend that non-adjuvant split-virion vaccine containing 7•5 μg haemagglutinin is adopted as the vaccine of choice against 2009 pandemic H1N1 in adolescents and adults. A two-dose schedule of this formulation might be needed in children."

This randomized controlled study investigated the administration of a pandemic H1N1 vaccine both alone and together with the normal seasonal influenza vaccine.

There were a total of 355 participants, including 203 adults (18 to 60 years) and 152 elderly people (over 60 years). There were two groups:

Group 1: 0.5 mL of the pandemic vaccine (Fluval P, a monovalent vaccine with 6 μg haemagglutinin per 0•5 mL and aluminium phosphate gel adjuvant); 178 recipients.