# Power of public health advice: Effectiveness and spillover effects of federal vaccine recommendations

## TL;DR

Federal vaccine recommendations significantly increased vaccination rates and had spillover effects, but coverage remains low among certain groups.

## Contribution

The study evaluates the effectiveness and spillover effects of federal vaccine recommendations and identifies demographic disparities in vaccination rates.

## Key findings

- The 2008 and 2010 vaccine recommendations increased vaccination likelihood by 20.9–26.5% in children and 5.2–6.6% in older adults.
- The 2009 H1N1 recommendation had a spillover effect, increasing influenza vaccination by 5.7–9.8% in younger adults.
- Low vaccination rates persist among specific demographic and socioeconomic groups.

## Abstract

This paper focuses on the national-level, inexpensive, demand-side vaccine policy—federal recommendations. It evaluates the effectiveness of 2008 and 2010 influenza vaccine recommendations, the spillover effect of the 2009 H1N1 vaccine recommendation on influenza vaccination, and heterogeneous policy effects across individual characteristics.

Observational study with before-after comparison assessing changes in vaccination following policy implementation.

We used nationally representative 2004–2015 NHIS data on 77,361, 23,653, and 238,866 individuals in age groups targeted by the 2008, 2009, and 2010 policies, respectively. Using the Linear Probability Model with fixed effects, we estimated policy effectiveness, spillover effects, and heterogeneous effects across individual characteristics.

Both 2008 and 2010 influenza vaccine recommendations boosted influenza vaccination likelihood by 20.9–26.5 % among children and 5.2–6.6 % among older adults. The 2009 H1N1 vaccine recommendation had a positive spillover effect, with a 5.7–9.8 % increase in influenza vaccination likelihood among younger adults. Low influenza vaccination likelihoods exist across demographic and socioeconomic characteristics: Children uninsured or privately insured, White, and low-income; Adults uninsured or publicly insured, White, African and Hispanic American, male, childless, self-reported poor or excellent health, low-educated, and low-income.

Future policies may address the cost barriers faced by the uninsured, and multi-level non-cost barriers experienced by privately insured children and publicly insured adults. Future policies may consider extending beyond the federal recommendation, such as implementing simultaneous anti-poverty policies, to achieve minimum coverage and utilize the spillover effects of one vaccine policy to maximize coverage of other vaccines. Future research may investigate potential policy spillover effects among influenza, COVID-19, RSV, and new vaccines.