Five Groups Targeted for Novel H1N1 Vaccination

Efforts to test the safety and efficacy of candidate vaccines against novel influenza A (H1N1) are well underway. An independent safety monitoring committee has recommended that trials of a candidate vaccine against the novel influenza A (H1N1) virus begin in children, according to the National Institute of Allergy and Infectious Diseases. At press time, vaccinations were scheduled to begin shortly in two trials being conducted through the agency's Vaccine and Treatment Evaluation Unit (VTEU) network. The safety monitoring committee reviewed data from more than 500 healthy adult and elderly volunteers enrolled in three VTEU trials of candidate novel H1N1 vaccines that began Aug. 7 and found no safety concerns in those trials that would preclude the start of pediatric trials, the NIAID said in a statement.

Once the candidate vaccines get the green light on safety and efficacy, a federal committee has advised that initial vaccination efforts focus on immunizing as many people as possible in five target groups: emergency medical personnel, pregnant women, children and adults aged 6 months to 24 years, caregivers and cohabitants of children younger than 6 months, and adults aged 25-64 years who are immunocompromised or who have chronic health conditions that may increase their flu risk.

Physicians are likely to have their hands full educating groups targeted for the novel influenza A (H1N1) immunization. Current seasonal influenza coverage among the five key groups is estimated at only 20%-50%, according to Dr. Anthony J. Fiore of the Center's for Disease Control and Prevention's Influenza Division.

The immunization recommendations were made by the Advisory Committee on Immunization Practices of the CDC at a special 1-day meeting. The primary targets for novel influenza A (H1N1) (nH1N1) immunization effort total about 159 million individuals in the United States. If vaccine demand exceeds availability, subgroups of the larger group, totaling 42 million people, should receive priority. The first subgroups— pregnant women and household and caregiver contacts for infants younger than 6 months of age—remain unchanged as a priority.

The next subgroups include health care and emergency personnel in direct contact with patients; children aged 6 months through 4 years of age; and children with chronic medical conditions. When vaccine availability is sufficient at the local level to routinely vaccinate initial target populations, a decision should be made in cooperation with state and local health authorities to vaccinate healthy adults aged 25-64 years first, then individuals aged 65 years and older. The last recommendation, in contrast to seasonal influenza accination recommendations, reflects the fact that older individuals thus far have been at lower risk for the novel influenza A H1N1 virus.

Dr. Doug Campos-Outcalt, the liaison to ACIP from the American Academy of Family Physicians, said that AAFP will likely support the prioritization scheme but may not issue a formal endorsement. Rather, the academy will probably provide a link on its website directing members to the CDC recommendations and “will be encouraging members to communicate and cooperate with state and local health departments, and to the extent they can, provide vaccines at their clinical sites,” Dr. Campos-Outcalt, associate head of family and community medicine at the University of Arizona, Phoenix, said in an interview. According to Dr. Fiore, new recommendations were needed because the federal government's 2007 pandemic vaccine priority guidance had been developed for the scenario of a severe pandemic with the potential for social disruption of critical infrastructure. The ACIP's Influenza Working Group concluded that current epidemiologic and immunologic evidence, combined with updated information on vaccine supply and availability timelines, indicated a need to revise recommendations that had been made during prepandemic planning.

In drafting the document that ACIP voted on, the working group assumed the following: that the severity of illness and groups at higher risk for infection or complications will be similar to what has already been observed; that the safety profile and antigen content of novel H1N1 vaccines will be similar to that of seasonal vaccine; and that adequate supplies of licensed unadjuvanted vaccine can be produced for all by approximately February 2010 but that enough vaccines for all will not be available before the next pandemic wave, expected this fall.