CPHA Canvax

Outcomes and unintended consequences of mandatory immunization programs

Noni E. MacDonald1, Eve Dubé2 and Daniel Grandt3

1. Department of Pediatrics, Dalhousie University, IWK Health Centre, Halifax, Nova Scotia.
2. Quebec National Institute of Public Health, Department of Anthropology, Laval University, 2400, avenue d'Estimauville, 3e étage, Québec, Québec.
3. Department of Internal Medicine, Klinikum Saarbruecken, Germany

Outbreaks of vaccine-preventable diseases occur even in high-income countries that have unrestricted and equitable access to immunizations. The reason is that vaccine uptake rates are not where they need to be for adequate control of vaccine-preventable diseases. As a consequence, several countries have discussed, enacted, or strengthened mandatory childhood immunization legislation (1-3). Mandatory immunization is seen as a “simple” solution to the problem.

In this CANVax in Brief, we provide an overview of a more detailed 2018 article on mandatory immunization (4) and some updates. We summarize the evidence of the effectiveness of mandatory immunizations as well as the evidence of unintended consequences.

There are surprisingly few systematic reviews, and very little comparative evidence on the outcomes of mandatory infant and childhood immunization programs. A 2016 systematic review of outcomes of mandates found only 11 before and after studies, and 10 studies comparing immunization rates in similar populations with and without mandates. Eighteen of these studies were in the USA, two in Canada and one in France (5). In 2018, a landscape review of the legislative environment for immunization was conducted in the 53 countries of the European region. Findings of this review showed a diversity of legislative frameworks for immunization (from recommendations to strong mandatory policies) with no clear evidence for the “best approach” to enhance vaccine uptake and acceptance (6). To interpret the results correctly, it is necessary to understand the differences that exist between mandatory immunization programs.

Scope and frameworks of mandatory immunization programs

In 2010, an expert group proposed the definition that a “mandatory” vaccine is one that every child in the country/state must receive by law without the option for the parent to accept or refuse it, independent of whether a legal or economical implication or sanction exists for the refusal (7). Mandatory immunization programs vary widely. There is neither a uniform method for establishing mandatory immunization programs nor a common scope for such programs.

With respect to scope, the mandate may apply to the entire country (Italy (2), France (2)), or to specific constituent states, territories or provinces (California, USA (2)), (Ontario, Canada (8)), or it may apply more narrowly to a defined subset of the population (9). Some programs cover most but not all of the WHO-recommended vaccines (e.g., Italy (2)), another may identify a limited range of vaccines (e.g., France, a specific list (2)), and another, only one vaccine (Belgium, polio vaccine (10)). Some may specify an age group or milestone such as on school entry (Italy on enrolment in kindergarten (2), California, USA, on school entry). With respect to flexibilities, some contain exemptions for medical contraindications only, while others include or previously included exemptions for religious and philosophical reasons (California, USA (3) and Australia (11) prior to 2016).

Strictness of application and levels of enforcement can vary, as can the body responsible for the enforcement of mandatory requirements (California, USA) (3). Other programs may not enforce the mandate at all (Serbia). The program may focus on financial incentives to encourage compliance (11), or impose penalties that may be financial or social (i.e., children can be precluded from daycare (Ontario, Canada1, Australia (11)), or school entry (California, USA). Individuals may be precluded from access to theme parks (California2), or they may be fined (Slovenia (10)) or even imprisoned (Uganda3).

There is a huge diversity of approaches to mandatory immunization required by law:

  • no enforcement, anyone can opt out without penalty (e.g., France before changes in 2018 (1)),

  • opt out due to personal or philosophical objection without penalty (e.g., Ontario, Canada before changes in 2016 (12)),

  • laws requiring parental education about immunization (rather than immunization itself); opt out with personal or philosophical objection but requires specific forms and notarization but no penalty for noncompliance (e.g., Ontario, Canada (8)),

  • laws requiring immunization but opt out with personal or philosophical objection that requires specific forms and added effort. There is a penalty for noncompliance and strict enforcement (e.g., Australia before changes in 2016 (11)),

  • laws requiring immunization with serious financial penalties or social restrictions; only allowing medical exemptions; strict enforcement (e.g., State of California USA post-2016 (3, 13), Australia after 2016 (11)).

1  https://www.ontario.ca/laws/regulation/150137#BK46
2  https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201520160SB277#content_anchor
3  https://ulii.org/node/27644

Outcomes of mandatory immunization programs

The 15 ethnic Republics that composed the former Union of Soviet Socialist Republics (USSR) and its communist neighbours all had very strong centralized public health systems with mandatory vaccination that enabled enforcement without question and was associated with high uptake rates. By 2018, however, much had changed with respect to childhood immunization in many of these countries. By 2018, Ukraine had the lowest childhood uptake rate in the WHO European Region; Serbia and Poland experienced protests against mandatory immunizations.

There have not been studies of mandates in high-income countries in jurisdictions with relatively high baseline rates or with mandates for child-care centres. In Belgium and Italy, some vaccines were mandatory and others were not, for historical reasons. Non-mandatory vaccines may have been perceived by the public and health care professionals as being less important and less necessary. In Italy, this differential program led to high coverage of the mandatory vaccines such as diphtheria, tetanus, poliomyelitis, hepatitis B, all greater than 93%, but lower than needed coverage of other recommended but not mandated vaccines, (e.g., measles 87% (2)). Measles outbreaks led Italy to move to broader mandatory immunization (2).

In Australia, in 2015, the No Jab No Pay amendment bill removed non-medical exemptions from existing vaccination requirements (11). By March 2018, these changes were associated with an increase in vaccine uptake among 5-year olds from 92.59% to 94.34%.

Unintended consequences of mandatory immunization programs

Mandatory immunization programs have the potential for unintended consequences. The removal of nonmedical exemptions (i.e. personal belief exemptions) has led to an increase in medical exemptions in California, USA (14) and in Australia (11). Regions with high previous rates of personal exemptions before the more restrictive laws were put in place appear to have higher rates of medical exemptions. This suggests a ‘gaming’ of the system. Disappointingly, the target population’s response has been to seek medical exemption, and not to accept immunization.

The effect of tightening the mandatory process in Ontario, such that more effort is needed to obtain a philosophical exemption, has not yet been assessed; but the ability to know who is immunized and not immunized is a boon to public health units who are concerned about the recent resurgence of measles in North America. 


There is no standard approach to mandatory immunizations. Which vaccines are included, age groups covered, program flexibility and rigidity (e.g., opportunities for opting out, penalties or incentives), and the degree of enforcement have to be considered. Mandatory immunization for childhood vaccines is not a guarantee that the problem of lower-than-desired vaccine uptake rates will be overcome. There is evidence that there is no strong difference in vaccination rates between countries that only recommend certain vaccinations and countries that mandate them (15). Furthermore, unintended consequences, such as a reduced acceptance rate of non-mandatory immunizations, have to be anticipated. In summary, rigid mandatory vaccination requirements may appear on first blush to be a “simple” solution to lower-than-needed vaccine uptake rates. However, the evidence does not support this conclusion. Addressing low vaccine uptake rates is a complex problem that needs a multipronged, more nuanced and tailored approach.

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