Field evaluation and post-vaccination monitoring for informed decision-making

The right evidence, at the right moment, can guide better decisions. 

As African swine fever (ASF) continues to affect pig production, animal health systems and safe trade worldwide, WOAH has published new guidelines to support evidence-based vaccine use. The Guidelines for African swine fever vaccines: field evaluation and post-vaccination monitoring provide practical guidance to help Members implement international standards and mitigate risks associated with substandard vaccines. 

Developed with experts from The Pirbright Institute and the Centre for Applied One Health Research and Policy Advice at City University of Hong Kong, the guidelines are now available and provide a practical, field-oriented reference for Veterinary Services, competent authorities and other stakeholders involved in vaccine deployment. 

Supporting evidence-based decisions in the field 

ASF vaccination is rapidly evolving. While vaccine candidates are under development and some live attenuated virus vaccines have received regulatory approval in certain countries, WOAH emphasises that only high-quality vaccines manufactured according to international standards should be used. Vaccination decisions must be grounded in reliable evidence and adapted to local epidemiological conditions. The guidelines support Members in generating and assessing this evidence, covering the design, implementation and evaluation of field studies, as well as the benefit–risk assessment that should precede any national or regional vaccination programme. Practical tools, including sample size calculators and recording form templates, are included to help users apply the guidance directly on the ground. 

From field trials to post-vaccination monitoring 

Running a field trial well requires getting many things right at once: clear case definitions, appropriate study designs, rigorous randomisation, consistent data collection and validated laboratory testing. The guidelines walk users through each of these elements, with worked examples where possible, to ensure that field evaluations generate evidence that is both reliable and usable for decision-making. 

Post-vaccination monitoring is equally important. The guidelines cover the systematic tracking of vaccine effectiveness under real-world conditions, alongside pharmacovigilance to detect side effects or adverse events. A dedicated three-step framework is provided to help countries set up and sustain monitoring systems, from establishing expected side effects and reporting channels to periodically evaluating and revising the programme. Genomic surveillance, including whole genome sequencing where feasible, is also recommended to detect potential reversion to virulence or recombination events over time. 

Vaccination as one tool among many 

These guidelines make clear that vaccination is not a standalone solution. It must be integrated  into comprehensive ASF prevention and control strategies, alongside biosecurity, surveillance and movement controls, tailored to each Member. 

Bringing technical guidance closer to Members 

Aligned with WOAH’s commitment to supporting Members in building robust animal health systems, the guidelines are designed to be adapted rather than applied rigidly. Countries with sufficient resources are encouraged to conduct their own field trials. Others can draw on data from countries with comparable production systems, with WOAH facilitating connections to relevant Reference Laboratories and Collaborating Centres. Transparency and data sharing are highlighted throughout, in keeping with the principles of the Terrestrial Animal Health Code. 

ASF is a transboundary disease, what happens in one country affects its neighbours. That is why the evidence generated through field trials needs to be shared, not kept in silos.  

Upcoming webinar 

To support the practical use of these guidelines, WOAH will host a webinar on 30 June 2026, bringing together the authors and selected Members to discuss the application of this resource. 

More information 

Guidelines for African swine fever vaccines: field evaluation and post-vaccination monitoring 

Contact: [email protected]

The continuing spread of African swine fever (ASF) is a matter of concern for the pig industry on a global scale, as no region is left unaffected. For many years, the lack of vaccine or effective treatment has made  the control of the disease very challenging. The research community has been working to develop an effective vaccine and recent announcements of modified live vaccines being approved or tested in some countries have raised hopes for the availability of new effective tools to contain the current ASF epidemic. Many countries are interested in using these candidate vaccines to help control ongoing outbreaks on their territory. 

In this context, the World Organisation for Animal Health (WOAH) stresses the importance of the use of only high-quality ASF vaccines with proven efficacy and safety, and which have been subject to regulatory evaluation and approval in accordance with WOAH international standards. 

The risks of using poor quality or non-compliant vaccines  

The use of non-compliant and poor-quality vaccines may not confer any protection against ASF and risks spreading vaccine viruses that could result in acute or chronic disease. Additionally, these vaccine viruses could also recombine with field strains to generate novel strains that could evade detection and result in acute, chronic and persistent ASF infections on farms. 

ASF vaccination should not be used as a stand-alone disease control intervention  

Regardless of vaccine efficacy, vaccination programmes should be implemented as part of a comprehensive prevention and control strategy, which should include other important control measures such as strict biosecurity, import measures and movement controls.

Vaccination, if used, should be conducted under a well-designed vaccination programme that takes into account, among other factors, the local epidemiology of the disease, the expected objectives of vaccination and the adequacy and sustainability of the relevant technical, financial and human resources. They should always include post-vaccination surveillance and monitoring as well as an exit strategy for the cessation of vaccination, as mentioned in WOAH international standards on vaccination (Chapter 4.18. of the Terrestrial Code).  

On the way to licensed ASF vaccines 

Convinced of the added value that the international recognition of high-quality vaccines would have, WOAH is monitoring the progress of several ASF vaccine candidates at various stages of development. Some countries have either approved or are conducting field trials for the use of modified live vaccine candidates against ASF genotype II.  

A new draft standard for the production of safe and effective vaccines against ASF has been proposed in the September 2023 report of the WOAH Biological Standards Commission. WOAH urges vaccine manufacturers and Members to consider these draft standards when developing and evaluating ASF vaccine candidates for regulatory approval and to provide their comments.  

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