The role of vaccine effectiveness on individual vaccination decisions and welfare

• Published date: 01 December 2023
• Author: Andrea Sorensen
• Date: 01 December 2023
• DOI: http://doi.org/10.1111/jpet.12644

Received: 25 March 2022

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Accepted: 29 March 2023

DOI: 10.1111/jpet.12644

ORIGINAL ARTICLE

The role of vaccine effectiveness on individual

vaccination decisions and welfare

Andrea Sorensen

Department of Economics, University of

St. Thomas, Saint Paul, Minnesota, USA

Correspondence

Andrea Sorensen, Department of

Economics, University of St. Thomas,

Saint Paul, MN 55105, USA.

Email: sore1019@stthomas.edu

Abstract

This paper examines a theoretical model designed to

characterize a static, individual vaccination decision

environment. I identify and characterize both equili-

brium and socially optimal vaccination behavior and

determine how this behavior changes as the effective-

ness of the vaccine changes. I also evaluate the

individual and social welfare implications of a change

in vaccine effectiveness. I find that under certain

conditions, an increase in vaccine effectiveness can

decrease the number of agents vaccinating in equili-

brium due to the positive external effects of vaccina-

tion. Notably, it is also possible for individual and total

welfare to decrease. This is an undesirable, and

perhaps unexpected, consequence of better vaccines.

Fortunately, welfare at the social optimum always

increases as vaccine effectiveness increases. However,

equilibrium behavior often falls short of the social

optimum due to the positive externalities created by

vaccinating.

KEYWORDS

externalities, health behavior, public economics

1|INTRODUCTION

Individual vaccination rates regularly fall below the recommended levels (Hill et al., 2021).

Since 2010, the Centers for Disease Control and Prevention (CDC) have recommended annual

influenza vaccination for everyoneat least 6 months ofage (Fiore et al.,2010). Each year we fall

short of this recommendation. During the 2020–2021 flu season, the CDC estimates that

J Public Econ Theory. 2023;25:1212–1228.wileyonlinelibrary.com/journal/jpet1212

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© 2023 Wiley Periodicals LLC.

coverage among adults was just 50.2%, and still just 58.6% among children. This was the highest

flu vaccination rate among adults in the past 10 years. The highest flu vaccination rate among

children inthe past10 years was63.7%in 2019–2020.

1

Rates for other childhood vaccines tend

to be higher, but still fall short of the recommended levels.

2

Furthermore, nonvaccinating

families tend to occur in geographic and social clusters, making the vaccination rates in some

areas substantially lower than the national averages, and allowing previously eradicated

diseases to emerge and spread (Tomeny et al., 2017).

Vaccines are playing a key role in the current COVID‐19 pandemic. As of August 2022,

67.2% of the US population was considered fully vaccinated. Of those fully vaccinated, only

48.2% had received the first booster dose.

3

If we can better understand the vaccination decision

environment, including individual incentives, externalities, and socially optimal behavior, it

may help in developing vaccination campaigns and policy interventions to boost vaccination

rates.

Additionally, the growing world health problem of “antimicrobial resistance”may place

even more importance on vaccines and the role that they play. According to the World Health

Organization (WHO), antimicrobial resistance is the “resistance of microorganisms to an

antimicrobial drug that was originally effective for treatment of infections caused by it.”

4

This is

a significant and growing problem in the United States and around the world. According to the

CDC, this problem has only been made worse by the COVID‐19 pandemic.

5

The WHO has gone

so far as to say that antimicrobial resistance “threatens the achievements of modern medicine”

(World Health Organization, 2014). Vaccines are predicted to be critically important in

addressing this problem by serving two important roles. First, vaccines can protect individuals

against illnesses that antimicrobials are no longer effective against. Second, when vaccines are

used as an alternative to antimicrobials, they “aid in stopping the trend of antimicrobial

resistance”(Joice & Lipsitch, 2013).

Because of this increasing importance of vaccines, it is critical that we understand the

vaccination decision environment and learn why observed behavior falls short of the target

levels. This includes understanding individuals' incentives, as well as how changes in the

parameters of the environment affect these incentives and overall welfare.

The model in this paper is an n‐player, simultaneous move game, designed to represent a

basic vaccination decision environment. This simultaneous move game was chosen for

simplification purposes, and to serve as a starting point for future work on dynamic vaccination

games. The static model is also useful in modeling vaccination decisions that occur without

feedback on others' vaccination decisions and before the disease is actively circulating, such as

annual influenza vaccines and many childhood vaccines. For example, when parents vaccinate

their children against diseases, like, measles, mumps, and rubella, these diseases are frequently

not observable in their area. Similarly, many individuals decide whether to receive a flu vaccine

in September and October, which is often before the flu is known to be circulating.

This model includes a single disease, a relatively simple model of contagion, and a single

vaccination decision for each agent. Here I consider only single‐dose vaccines, although the

1

CDC. Flu Vaccination Coverage, the United States, 2020–2021. Influenza Season. 2021; Available from: https://www.cdc.gov/flu/

fluvaxview.index.htm.

2

DTP, DT, or DTaP—83.4%; Polio—91.3%; MMR—91.1%; Hep B—90.5%; PCV—81.8% (www.cdc.gov/nchs/fastats/immunize).

3

CDC. Covid Data Tracker. Atlanta, GA: US Department of Health and Human Services, CDC, 2022. August 11.

4

www.who.int/mediacentre/factsheets/fs194/en/

5

CDC. COVID‐19: US Impact on Antimicrobial Resistance, Special Report. 2022. Atlanta, GA: US Department of Health and Human

Services, CDC; 2022.

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