CDC Advisers Say Half of U.S. Population Should Get Pandemic Vaccine
BETHESDA, MD 30 July 2009—Advisers to the Centers for Disease Control and Prevention (CDC) yesterday recommended that about half of the U.S. population seek immunization when the first batches of pandemic H1N1 influenza virus vaccine become available later this year.
In all, CDC’s Advisory Committee on Immunization Practices (ACIP) recommended five groups to receive the initial doses of vaccine. These groups are pregnant women, household contacts of children less than six months of age, health care workers and emergency medical services personnel, people age 6 months through 24 years, and adults age 25–64 years with chronic conditions that increase the risk of influenza-related complications.
“These are groups that had higher risk of disease or who had greater burden of complications” so far during the pandemic, said Anne Schuchat, director of CDC’s National Center for Immunization and Respiratory Diseases, at a media briefing after the advisory meeting. In all, about 159 million people are included in the targeted groups.
Initial epidemiologic data suggested that obese people could be at increased risk for death after infection with the pandemic H1N1 2009 influenza virus. But newer data indicate that obesity is not an independent risk factor for death, Anthony Fiori of CDC’s influenza division told the committee members.
Notably absent from the priority list is the 65-and-older population, a group at high priority for vaccination against seasonal influenza viruses. The advisers agreed that epidemiologic data show that the H1N1 2009 influenza virus targets younger age groups.
“The H1N1 outbreak so far has, to a large extent, spared [the elderly] population,” Schuchat said.
The advisers recommended that once local public health officials believe the demand for vaccine has largely been met among the priority groups, efforts should be made to vaccinate adults 25&ndash64 years. Only after the demand for vaccine has been met among these adults should those age 65 or older be targeted for vaccination.
The overall consensus was to define the targeted groups for vaccination as broadly as possible, taking into account the estimated initial vaccine supply.
Several committee members expressed concern that many people who should be protected may not seek vaccination if the prioritization plan is too narrow or complex.
“Tight prioritization will result in vaccine being unused,” warned William Shaffner, president-elect of the National Foundation for Infectious Diseases. “When you have it, just give it.”
Federal officials are projecting that at least 120 million doses of monovalent, licensed H1N1 2009 influenza vaccine will be available in October, and about 80 million doses will become available each month thereafter through next spring.
But more than 300 million doses of vaccine will probably be required to fully protect the initially targeted population.
“The working assumption is that you need two doses for everyone,” Fiori said.
Fiori said that during a normal influenza season, “about 20–50%” of those who should get vaccinated actually do so. Federal planners said that they do not know what the demand for H1N1 2009 influenza vaccine will be, but they do not expect all those targeted to seek vaccination.
Because of uncertainties about vaccine supply and demand, the committee was asked to consider whether certain subgroups should be targeted if there is a serious vaccine shortfall.
In this case, the group decided, vaccine should be recommended for five subgroups: pregnant women, close contacts of children younger than 6 months of age, health care and emergency services personnel with direct patient contact, children 6 months through 4 years of age, and children age 5–18 years with chronic medical conditions.
Fiori said about 42 million Americans would be targeted for vaccination under this plan.
A final recommendation from the advisers was to keep vaccinating priority patients as they arrive and not hold vaccine in reserve for patients for their second dose.
“Don’t set aside in your mind or your refrigerator a second dose,” Fiori said.
The federal government is stockpiling adjuvants for emergency use if clinical data indicate that these pharmacologic agents are needed to boost immunity and, potentially, stretch the vaccine supply.
“The decision to use or not use adjuvants has not been made at this point, but we want to be prepared for the worst-case scenario,” Robin Robinson, director of the Biomedical Advanced Research and Development Authority, told the advisers.
But the committee members based their recommendations on the monovalent, unadjuvanted vaccines that FDA has indicated can be licensed as a strain change to currently approved influenza vaccines. Licensure as a strain change is the regulatory path used each year when manufacturers prepare updated versions of trivalent seasonal influenza vaccines.
Kathy Neuzil, chair of ACIP’s influenza working group emphasized that no one knows how the pandemic will continue to unfold. She said plans for administering vaccines “may need to be reconsidered as the pandemic progresses.”
