FOI release

FOI - Vaccine strains currently or recently employed in the UK

Published 30 October 2025

ATI1095 Request

• What have been the most commonly employed vaccine strains and/or trade names against FHV-1 in the UK over the past 10 years?

• Is there any available data on the spatial distribution of feline vaccine use within the UK?

• When was the F2 vaccine strain first introduced or made available in the UK market?

• Which vaccine strain has been most frequently associated with reported adverse reactions?

• Have there been any reports suggesting reversion to virulence of any of the vaccine strains currently in use?

Our reply

What have been the most commonly employed vaccine strains and/or trade names against FHV-1 in the UK over the past 10 years?

Details on vaccines used to reduce the clinical signs of FHV-1 can be found in the Summary of Products Characteristics (SPCs) for these vaccines by searching for ‘Feline viral rhinotracheitis virus’ in the ‘Active Substance’ field of the Product Information Database - Search.

The two most commonly sold vaccine strains to reduce clinical signs of FHV-1 in the United Kingdom in the last 10 completed calendar years (2014-2024) are F2 and G2620A. This information is obtained from sales data provided by the Marketing Authorisation Holder (MAH) to the VMD. Please note that the VMD does not collect usage data, and therefore the information provided does not account for any doses purchased that expired or were otherwise disposed of without being administered.

All vaccines involving FHV-1 were authorised before 2015. Therefore, no new vaccine strains or trade names have been authorised over the past 10 years.

Is there any available data on the spatial distribution of feline vaccine use within the UK?

The VMD do not hold information on individual sales to veterinary practices as the onward supply of a vaccine is a commercial decision for the Marketing Authorisation Holder. Therefore, we are unable to provide details of spatial distribution of feline vaccine use in the UK.

When was the F2 vaccine strain first introduced or made available in the UK market?

The first authorised vaccines to contain feline herpesvirus F2 strain were those in the Purevax range, specifically Purevax RC, Purevax RCP, Purevax RCPCh, Purevax RCPCh FeLV and Purevax RCP FeLV. All of these products were first authorised in February 2005. Currently these products are authorised in GB and centrally authorised in the EU. Information on these products can be found in the VMD’s Product Information Database.

Which vaccine strain has been most frequently associated with reported adverse reactions?

The frequency of adverse events is defined using the following convention:

• very common (more than 1 in 10 animals treated displaying adverse reaction(s))

• common (more than 1 but less than 10 animals in 100 animals treated)

• uncommon (more than 1 but less than 10 animals in 1,000 animals treated)

• rare (more than 1 but less than 10 animals in 10,000 animals treated)

• very rare (less than 1 animal in 10,000 animals treated, including isolated reports)

The total number of doses sold, and the total number of adverse events are used to determine frequency. This allows the number of adverse events to be contextualised in relation to the volume of sales. The number of adverse events includes reports:

• where more than one product was used
• when the product was used off-label, that is using a medicine in a way that is not specified on the product’s label, including prescribing of unauthorised medicines following the cascade
• where the reporters, medical professionals or MAH did not consider an association between the product administration and the adverse event to be likely
• where, on further evaluation, there were other reasons for the adverse reaction occurring such as underlying illnesses or an alternative cause for the clinical signs seen

Both the F2 and G2620A strains have adverse events occurring rarely following administration, they both have around 3 adverse events occurring for every 10,000 doses sold.

Although information published can be useful to provide a general overview of a VMP, it is important for any clinical decisions regarding the use of a VMP to be based on a risk/benefit discussion specific to the animal or group of animals being administered the VMP. An overall frequency of an adverse event occurring for a VMP does not reflect the actual risk for an individual animal, as there are many individual factors that may contribute to the likelihood of an adverse event occurring. Where relevant we would recommend owners seeking advice from their veterinary practice, especially prior to starting or stopping a VMP.

Data published by the VMD are not subject to independent verification and the VMD does not guarantee their accuracy. Figures may be different to those provided by different regulatory authorities, pharmaceutical companies, and other authorities within the United Kingdom.

Have there been any reports suggesting reversion to virulence of any of the vaccine strains currently in use?

All adverse events submitted to the VMD have their clinical signs coded using the Veterinary Dictionary for Drug Regulatory Activities (VeDDRA).

There was 1 report in our databases which contained the VeDDRA Preferred Term “Suspected reversal to virulence”. The report involved an FHV-1 vaccine with the FVRm strain, 8 kittens were vaccinated with this and another non-FHV-1 vaccine, within 24 hours all had upper respiratory signs, laboratory reports indicated Feline Herpesvirus was present in the sample, however no strain details were provided, therefore a field strain infection cannot be ruled out.

Evaluation of adverse event reports is dependent on the accuracy and quality of data received within adverse event reports from veterinary professionals and animal owners.