The number of children hospitalized for the flu in Connecticut plummeted after a recent statewide vaccination mandate, according to a new report co-authored by Yale investigators.

In September 2010, Connecticut became the second U.S. state to require that all children from six months to six years of age receive a dose of influenza vaccine each year prior to Jan. 1 in order to attend a state-licensed childcare program. Despite anticipated public resistance towards the program, the investigators found that the mandate decreased hospitalization rates and increased vaccination rates, said James Hadler, lead study author and clinical professor of epidemiology at the Yale School of Medicine.

“Our study demonstrated the feasibility [of making] day care centers safer,” Hadler said. “We hope that other states will consider that [mandated vaccinations for day-care attending children] is something that can and should be done. Connecticut and New Jersey have broken the ice on this issue and hopefully others will follow.”

According to the study, Connecticut’s vaccination rate for children aged six months to six years increased significantly after the mandate, spiking from 67.8 percent during the 2009–’10 influenza season to 84.1 percent during the 2012–’13 flu season. Compared to nine other states without mandates, Connecticut also saw the greatest percentage decrease in the influenza-associated hospitalization rate among children aged four years and younger.

Even though the study only looked at hospitalization rates of young children, Hadler said hospitalization rates for the entire community likely decreased as well. Even though the mandate applied only to young children, other studies have demonstrated that protecting a subset of the population decreases circulation of the virus more generally, Hadler said.

Day care centers regularly check all immunization and medical records at the start of each school year, and influenza vaccine is typically only available in late September. Although this late release creates more logistical challenges for health administrators, Hadler said the study demonstrated that a mandated influenza vaccine is feasible.

“People don’t think about influenza conventionally as a deadly disease like measles for example,” said Kimberly Yousey-Hindes, a study author and epidemiologist with the Yale School of Public Health. “Now that we have gotten those illnesses under control, we can move onto other diseases such as influenza which can be just as deadly especially in young children and the elderly.”

In 2009, the Centers for Disease Control and Prevention recommended that all people older than six months receive a yearly influenza immunization. Christina Tan, assistant commissioner for epidemiology in the New Jersey Department of Health, called the recommendation an important public health initiative, adding that states will continue to independently determine whether to adopt a mandate similar to that in Connecticut.

While a mandate for an annual vaccine may at first seem like a financial burden to the uninsured, Tan said the CDC’s Vaccination for Children program provides the shots at no cost to those in need.

Public health officials nationwide are considering broader mandates, Hadler said. In Connecticut, some individual hospitals have already mandated that employees receive the vaccination, and state officials have recommended that all hospital staff receive the vaccine.

A CDC report from March 22, 2013 indicated that of the 105 children who died from the flu in the 2012 to 2013 flu season, 90 percent had not been vaccinated.