An average of 20,000 children younger than 5 years old are hospitalized each year because of flu complications nationwide. To reduce the risk of hospitalization from complications of influenza, the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC) now recommend routine annual influenza vaccination of children older than 6 months. In September 2010, Connecticut became the second U.S. state (after New Jersey) to implement regulations requiring that all children aged 6–59 months receive at least 1 dose of the influenza vaccine annually to attend a licensed child care program. One year later, this requirement was expanded to include all children aged 24–59 months who were enrolled in a preschool program.

The goal of requiring that all Connecticut children receive at least 1 dose of influenza vaccine each year to attend a licensed child care program and preschool setting is to reduce influenza transmission and decrease influenza-associated hospitalizations statewide.

Requiring vaccination for admission into a licensed child care program or preschool program has helped to increase vaccination rates among children in Connecticut and reduced serious morbidity from influenza statewide.

To evaluate the impact of this regulation on vaccination levels and influenza-associated hospitalizations during the 2012–13 influenza season, vaccination data from U.S. and Connecticut surveys and the Emerging Infections Program (EIP) were analyzed. After the regulation took effect, vaccination rates among Connecticut children aged 6–59 months increased from 67.8% during the 2009–10 influenza season to 84.1% during the 2012–13 season. During the 2012–13 influenza season, Connecticut had the greatest percentage decrease (12%) in the influenza-associated hospitalization rate from 2007–08 among children aged ≤4 years across all 11 EIP surveillance sites. Furthermore, the ratio of the influenza-associated hospitalization rates among children aged ≤4 years to the overall population rate (0.53) was lower than for any other EIP site.

Data from multiple surveys were used to estimate vaccination rates among children aged 6–59 months in Connecticut. During 2009–10, the season before the state's influenza vaccination requirement took effect, 67.8% (95% CI = 61.1%–74.5%) of Connecticut children aged 6–59 months received a vaccination for seasonal influenza. During the 2012–13 season, the seasonal influenza vaccination rate increased to 84.1% (CI = 78.2%–90.0%). The increase of 16.3 percentage points in Connecticut was greater than the national increase of 11.9 percentage points (from 57.9% to 69.8%), comparing the same age group for the same two seasons; however the difference is not statistically significant. Among 11 EIP sites during the 2007–08 influenza season, Connecticut ranked third-highest in incidence of influenza-associated hospitalizations among children aged ≤4 years (58.6 per 100,000). During the 2012–13 season, Connecticut dropped to seventh (51.5 per 100,000) and was one of only two sites to record a decrease in incidence (12%) among children aged ≤4 years.

As of December 31, 2012, 87.1% of children enrolled in licensed child care settings had received ≥1 dose of influenza vaccine for the 2012–13 season. In total, 5.1% of children enrolled were listed as exempt from influenza vaccination for either religious or medical reasons, compared with 1.7% for all other vaccinations.