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Equine herpesvirus vaccine

ISSN 2398-2977

Synonym(s): EHV vaccine



  • Equine herpesvirus vaccine.
  • Two currently marketed in the UK:
    • Equip EHV1,4 (formally Duvaxyn EHV 1,4).
    • Equilis Resequin (combined with influenza virus).

Class of drug

  • Inactivated vaccine.
For further information in the UK see the Horserace Betting Levy Board's Codes of Practice on Equine Herpes Virus.


Chemical name

  • Equip EHV 1,4: contains inactivated EHV-1 strain 438/77 and inactivated EHV-4 strain 405/76; carbopol as adjuvant.
  • Equilis Resequin: contains inactivated EHV-1 strain RAC-H and inactivated EHV-4 strain 2252; preservative sodium timerfonate; traces of antibiotic, ovalbumin and formaldehyde; aluminium hydroxide and ImmunostimTM to enhance immunizing effect.

Physical properties

  • Vaccine inactivated by formaldehyde or ß propionate.

Storage requirements

Store according to manufacturer's recommendations.
  • Usual storage procedures:
    • Refrigerate at 2-8°C/35.6-46.4°F.
    • Do not freeze.
    • Protect from light.



Vaccine does not prevent infection, but rather limits the severity of clinical signs and extent of shedding of infectious virus.


  • Horses and ponies older than 5 months (ideally all horses in same yard/herd should be vaccinated).
  • Pregnant mares, to reduce the risk of EHV-1 associated abortion.
  • Maiden or barren mares in contact with pregnant mares.
  • Other horses older than 5 months in contact with pregnant mares.


Do not mix with

  • Other vaccines or drugs.

Routes of administration

  • Deep IM injection.


Basic dose

  • Single dose from 5 months of age, with second dose after 4-6 weeks.
  • Booster dose very 6 months.
  • See individual preparation details for exact vaccine program and dosage.

Variation to normal dose

  • Can vaccinate from 3 months of age if there is increased infection risk, eg foal received insufficient colostrum or risk of early exposure to field infection with EHV-1/4.
  • When combined with influenza vaccine, first dose not before 6 months of age.

Timing of administration

  • Foals should be vaccinated from 4 months of age.
  • Pregnant mares: 3 doses at 5, 7 and 9 months gestation.




  • In foals <5 months.
  • Early pregnancy.
  • Do not mix with other vaccines.

Use with care

  • Oil-based vaccines can cause pain (no longer available in UK).
Accidental self-injection may result in severe swelling and ischemic necrosis. Seek medical attention promptly.


with other drugs

  • Do not vaccinate within 4 weeks of receiving immunosuppressive drugs, eg corticosteroids.

with diagnostic tests

  • Seroconversion in response to vaccination is difficult to distinguish from seroconversion as a response to recent infection or carrier status.

Withdrawal Periods

Adverse Reactions

Effects of overdosage

  • Not reported.

Other reported reactions

  • Suggested relationship between vaccination and field challenge and the development of the neurological form. No research to confirm or deny this.
  • Local and systemic reactions following recent respiratory infection with herpesvirus Respiratory: EHV infection.
  • Local reactions include focal swelling at site of injection, usually <7 cm in diameter and resolve within 10 days.
  • May have increase in body temperature by up to 1.5degC on the day after vaccination.

Reporting of reactions

  • In the UK, report using the Suspected Adverse Reaction Surveillance Scheme (SARSS).


  • Focal swelling usually resolve within 10 days without treatment.
  • Anaphylactic/allergic reaction: soluble glucocorticoid IV or adrenalin IM.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Paillot R, Case R, Ross J, Newton R & Nugent J (2008) Equine herpes virus-1: virus, immunity and vaccine. Open Vet Sci J 2, 68-91 BenthamOpen (full text pdf).

Other sources of information

  • Horserace Betting Levy Board (2019) Codes of Practice. 5th Floor, 21 Bloomsbury Street, London WC1B 3HF, UK. Tel: +44 (0)207 333 0043; Fax: +44 (0)207 333 0041; Email: enquiries@hblb.org.uk; Website: http://codes.hblb.org.uk.
  • Holmes M A, Townsend H G, Hussey S et al (2003) Immune Responses to Commercial Equine Vaccines. In: Proc AAEP Convention. 49, pp 224-226.