POM-V
Prescription Required
Improvac Solution for Injection for Pigs
Active ingredient: 2-10-GnRF-Diphtheria Toxoid conjugate
Form
Injection
Species
Pigs
Manufacturer
Zoetis UK Limited
VMD MA No.
42058/5028
What it's used for
Male pigs: Induction of antibodies against GnRF to produce a temporary immunological suppression of testicular function. For use as an alternative to physi...
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Clinical information
Improvac Solution for Injection for Pigs — SPC Details
Source: VMD Summary of Product Characteristics (SPC). Last updated 27 Mar 2026.
Male pigs:
Induction of antibodies against GnRF to produce a temporary immunological
suppression of testicular function. For use as an alternative to physical castration for
the reduction of boar taint caused by the key boar taint compound androstenone, in
entire male pigs following the onset of puberty.
Another key contributor to boar taint, skatole, may also be reduced as an indirect
effect. Aggressive and sexual (mounting) behaviours are also reduced.
The onset of immunity (induction of anti-GnRF antibodies) can be expected within 1
week post second vaccination. Reduction of androstenone and skatole levels has
been demonstrated from 4 to 6 weeks post second vaccination. This reflects the time
needed for clearance of boar taint compounds already present at the time of
vaccination as well as the variability of response between individual animals.
Reduction of aggressive and sexual (mounting) behaviours can be expected from 1
to 2 weeks post second vaccination.
Revised: February 2025
AN: 03536/2024
Female pigs:
Induction of antibodies against GnRF to produce a temporary immunological
suppression of ovarian function (suppression of oestrus) in order to reduce the
incidence of unwanted pregnancies in gilts intended for slaughter, and to reduce the
associated sexual behaviour (standing oestrus).
The onset of immunity (induction of anti-GnRF antibodies) can be expected within 1
week post second vaccination. Reduction of sexual behaviour (standing oestrus) can
be expected from 1 to 2 weeks post second vaccination. The duration of
immunological suppression of ovarian function has been demonstrated for 9 weeks
after the second vaccination.
Induction of antibodies against GnRF to produce a temporary immunological
suppression of testicular function. For use as an alternative to physical castration for
the reduction of boar taint caused by the key boar taint compound androstenone, in
entire male pigs following the onset of puberty.
Another key contributor to boar taint, skatole, may also be reduced as an indirect
effect. Aggressive and sexual (mounting) behaviours are also reduced.
The onset of immunity (induction of anti-GnRF antibodies) can be expected within 1
week post second vaccination. Reduction of androstenone and skatole levels has
been demonstrated from 4 to 6 weeks post second vaccination. This reflects the time
needed for clearance of boar taint compounds already present at the time of
vaccination as well as the variability of response between individual animals.
Reduction of aggressive and sexual (mounting) behaviours can be expected from 1
to 2 weeks post second vaccination.
Revised: February 2025
AN: 03536/2024
Female pigs:
Induction of antibodies against GnRF to produce a temporary immunological
suppression of ovarian function (suppression of oestrus) in order to reduce the
incidence of unwanted pregnancies in gilts intended for slaughter, and to reduce the
associated sexual behaviour (standing oestrus).
The onset of immunity (induction of anti-GnRF antibodies) can be expected within 1
week post second vaccination. Reduction of sexual behaviour (standing oestrus) can
be expected from 1 to 2 weeks post second vaccination. The duration of
immunological suppression of ovarian function has been demonstrated for 9 weeks
after the second vaccination.
Subcutaneous use.
Entire male pigs from 8 weeks of age onwards should be vaccinated with 2 doses of
2 ml at least 4 weeks apart, with the second dose normally given 4 to 6 weeks prior
to slaughter. If slaughter is intended to be later than 10 weeks after the second dose
a third dose should be given 4 to 6 weeks before the planned slaughter date. In case
of suspected misdosing, the animal should be revaccinated immediately.
Female pigs from 10 weeks of age onwards should be vaccinated with 2 doses of 2
ml administered 4 to 8 weeks apart. In case of suspected misdosing, the animal
should be revaccinated immediately.
Administer by subcutaneous injection in the neck, immediately behind the ear, using
a safety vaccinator. As a guide, use a short needle (16G, typically) to give 12 to 15
mm penetration. To avoid intramuscular deposition and lesions, it is recommended to
use a shorter needle to give 5 mm to 9 mm penetration in undersized pigs and pigs
younger than 16 weeks of age. Note that when using a safety vaccinator part of the
needle will be covered by the needle guard and will not penetrate the pig. Depending
on the type of safety vaccinator, pressure may also be put on the skin and push the
needle a few millimetres deeper into the tissue. These circumstances should be
taken into account when choosing an appropriate needle length. Follow instructions
for proper subcutaneous injection provided with the device used. Avoid introduction
of contamination. Avoid injecting pigs that are wet and dirty. Allow the vaccine to
reach room temperature (15-25 before administration.
Entire male pigs from 8 weeks of age onwards should be vaccinated with 2 doses of
2 ml at least 4 weeks apart, with the second dose normally given 4 to 6 weeks prior
to slaughter. If slaughter is intended to be later than 10 weeks after the second dose
a third dose should be given 4 to 6 weeks before the planned slaughter date. In case
of suspected misdosing, the animal should be revaccinated immediately.
Female pigs from 10 weeks of age onwards should be vaccinated with 2 doses of 2
ml administered 4 to 8 weeks apart. In case of suspected misdosing, the animal
should be revaccinated immediately.
Administer by subcutaneous injection in the neck, immediately behind the ear, using
a safety vaccinator. As a guide, use a short needle (16G, typically) to give 12 to 15
mm penetration. To avoid intramuscular deposition and lesions, it is recommended to
use a shorter needle to give 5 mm to 9 mm penetration in undersized pigs and pigs
younger than 16 weeks of age. Note that when using a safety vaccinator part of the
needle will be covered by the needle guard and will not penetrate the pig. Depending
on the type of safety vaccinator, pressure may also be put on the skin and push the
needle a few millimetres deeper into the tissue. These circumstances should be
taken into account when choosing an appropriate needle length. Follow instructions
for proper subcutaneous injection provided with the device used. Avoid introduction
of contamination. Avoid injecting pigs that are wet and dirty. Allow the vaccine to
reach room temperature (15-25 before administration.
Do not use in breeding animals. Please also refer to section 4.7.
Male pigs (from 8 weeks of age). Female pigs (from10 weeks of age).
Very common
(>1 animal / 10 animals treated):
injection site swelling 2-8 cm in
diameter
a
elevated temperature (around 0.5 °C
during the 24 hours after vaccination in
males and around 1.0 – 1.3 °C during
the 24 hours after vaccination in
females)
Very rare
(<1 animal / 10,000 animals treated,
including isolated reports):
anaphylactoid reaction (dyspnoea,
collapse, cyanosis and hypersalivation
associated with or without twitching or
emesis) within a few minutes after
vaccination with a duration of up to 30
minutes
b
a
When administered to pigs at the youngest recommended age (8 weeks), injection
site swellings of up to 4 x 8 cm are very commonly observed. A gradual resolution of
the local reactions occurs, but in 20 – 30% of the animals these may persist for more
than 42 days.
When administered to older pigs (14–23 weeks of age) injection site swellings may
occur very commonly. Injection site swellings ranging from 2 cm to 5 cm in diameter
are commonly observed, and injection site reactions at slaughter are commonly
observed if the second vaccination is given only 4 weeks before slaughter.
b
In a small number of animals, death occurred following the reaction, however most
animals recovered without treatment and did not appear to react to subsequent
vaccinations.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian, to
either the marketing authorisation holder <or its local representative or the national
competent authority via the national reporting system>. See also the last section of
the package leaflet for respective contact details.
Very common
(>1 animal / 10 animals treated):
injection site swelling 2-8 cm in
diameter
a
elevated temperature (around 0.5 °C
during the 24 hours after vaccination in
males and around 1.0 – 1.3 °C during
the 24 hours after vaccination in
females)
Very rare
(<1 animal / 10,000 animals treated,
including isolated reports):
anaphylactoid reaction (dyspnoea,
collapse, cyanosis and hypersalivation
associated with or without twitching or
emesis) within a few minutes after
vaccination with a duration of up to 30
minutes
b
a
When administered to pigs at the youngest recommended age (8 weeks), injection
site swellings of up to 4 x 8 cm are very commonly observed. A gradual resolution of
the local reactions occurs, but in 20 – 30% of the animals these may persist for more
than 42 days.
When administered to older pigs (14–23 weeks of age) injection site swellings may
occur very commonly. Injection site swellings ranging from 2 cm to 5 cm in diameter
are commonly observed, and injection site reactions at slaughter are commonly
observed if the second vaccination is given only 4 weeks before slaughter.
b
In a small number of animals, death occurred following the reaction, however most
animals recovered without treatment and did not appear to react to subsequent
vaccinations.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian, to
either the marketing authorisation holder <or its local representative or the national
competent authority via the national reporting system>. See also the last section of
the package leaflet for respective contact details.
Please refer to section 4.3 and section 4.7.
Vaccinate healthy animals only.
i) Special precautions for use in animals
Improvac has been shown to be safe in male and female pigs from 8 weeks of age
onwards. In male pigs, the recommended time for slaughter is 4 to 6 weeks after the
final injection. If male pigs cannot be slaughtered within this recommended period,
the available trial data support that pigs may still be sent for slaughter up to 10 weeks
after the final injection with minimal risk of boar taint. An increasing proportion will
return to normal function after this time. As skatole levels are not fully dependent on
sexual status, both dietary and hygiene management procedures to reduce skatole
levels are also important. In female pigs, the duration of immunological suppression
of ovarian function has been demonstrated for 9 weeks after the second vaccination.
An increasing proportion of female pigs may be expected to return to normal function
after this time.
ii) Special precautions to be taken by the person administering the veterinary
medicinal product to animals
Accidental self-injection may produce similar effects in people to those seen in
pigs. These may include a temporary reduction in sexual hormones and
reproductive functions in both men and women and an adverse effect on
pregnancy. The risk of these effects occurring is greater after a second or
subsequent accidental injection than after a first injection.
Special care should be taken to avoid accidental self-injection and needle stick
injury when administering the veterinary medicinal product. The veterinary
medicinal product must only be used with a safety vaccinator, which has a dual
Revised: February 2025
AN: 03536/2024
safety system providing both a needle guard and a mechanism to prevent
accidental operation of the trigger.
The veterinary medicinal product must not be administered by pregnant
women or those who may be pregnant at that time.
In case of eye contact, rinse immediately with copious amounts of water. In case of
skin contact, wash immediately with soap and water.
Advice to the user in the event of accidental self-injection:
Accidental injection/self-injection may result in severe pain and swelling, particularly if
injected into a joint or finger, and in rare cases could result in the loss of the affected
finger if prompt medical attention is not given.
In the event of accidental self-injection, wash the injury thoroughly with clean running
water. Seek prompt medical adviceeven if only a very small amount is injected and
take the package leaflet with you. If pain persists for more than 12 hours after
medical examination, seek medical advice again. Do not administer the veterinary
medicinal product in the future.
Advice to the physician:
Accidental self-injection could temporarily affect reproductive physiology of both men
and women and may adversely affect pregnancy. If self-injection with Improvac is
suspected, reproductive physiology should be monitored by assay of testosterone or
oestrogen levels (as appropriate). The risk of a physiological effect is greater after a
second or subsequent accidental injection than after a first injection. Clinically
meaningful suppression of gonadal function should be managed with supportive
endocrine replacement therapy until normal function returns. The patient should be
advised not to administer Improvac and/or any other veterinary medicinal products
with similar action in the future.
Even if small amounts have been injected, accidental injection with this product can
cause intense swelling, which may, for example, result in ischaemic necrosis and
even the loss of a digit. Expert, PROMPT, surgical attention is required and may
necessitate early incision and irrigation of the injected area, especially where there is
involvement of finger pulp or tendon.
Special precautions for the protection of the environment
Not applicable.
iii) Other precautions:
The safety and efficacy of the veterinary medicinal product in non-target species
such as horses has not been evaluated. Adverse events have been observed in
horses including serious anaphylactic type reactions which have led to fatalities.
Revised: February 2025
AN: 03536/2024
Vaccinate healthy animals only.
i) Special precautions for use in animals
Improvac has been shown to be safe in male and female pigs from 8 weeks of age
onwards. In male pigs, the recommended time for slaughter is 4 to 6 weeks after the
final injection. If male pigs cannot be slaughtered within this recommended period,
the available trial data support that pigs may still be sent for slaughter up to 10 weeks
after the final injection with minimal risk of boar taint. An increasing proportion will
return to normal function after this time. As skatole levels are not fully dependent on
sexual status, both dietary and hygiene management procedures to reduce skatole
levels are also important. In female pigs, the duration of immunological suppression
of ovarian function has been demonstrated for 9 weeks after the second vaccination.
An increasing proportion of female pigs may be expected to return to normal function
after this time.
ii) Special precautions to be taken by the person administering the veterinary
medicinal product to animals
Accidental self-injection may produce similar effects in people to those seen in
pigs. These may include a temporary reduction in sexual hormones and
reproductive functions in both men and women and an adverse effect on
pregnancy. The risk of these effects occurring is greater after a second or
subsequent accidental injection than after a first injection.
Special care should be taken to avoid accidental self-injection and needle stick
injury when administering the veterinary medicinal product. The veterinary
medicinal product must only be used with a safety vaccinator, which has a dual
Revised: February 2025
AN: 03536/2024
safety system providing both a needle guard and a mechanism to prevent
accidental operation of the trigger.
The veterinary medicinal product must not be administered by pregnant
women or those who may be pregnant at that time.
In case of eye contact, rinse immediately with copious amounts of water. In case of
skin contact, wash immediately with soap and water.
Advice to the user in the event of accidental self-injection:
Accidental injection/self-injection may result in severe pain and swelling, particularly if
injected into a joint or finger, and in rare cases could result in the loss of the affected
finger if prompt medical attention is not given.
In the event of accidental self-injection, wash the injury thoroughly with clean running
water. Seek prompt medical adviceeven if only a very small amount is injected and
take the package leaflet with you. If pain persists for more than 12 hours after
medical examination, seek medical advice again. Do not administer the veterinary
medicinal product in the future.
Advice to the physician:
Accidental self-injection could temporarily affect reproductive physiology of both men
and women and may adversely affect pregnancy. If self-injection with Improvac is
suspected, reproductive physiology should be monitored by assay of testosterone or
oestrogen levels (as appropriate). The risk of a physiological effect is greater after a
second or subsequent accidental injection than after a first injection. Clinically
meaningful suppression of gonadal function should be managed with supportive
endocrine replacement therapy until normal function returns. The patient should be
advised not to administer Improvac and/or any other veterinary medicinal products
with similar action in the future.
Even if small amounts have been injected, accidental injection with this product can
cause intense swelling, which may, for example, result in ischaemic necrosis and
even the loss of a digit. Expert, PROMPT, surgical attention is required and may
necessitate early incision and irrigation of the injected area, especially where there is
involvement of finger pulp or tendon.
Special precautions for the protection of the environment
Not applicable.
iii) Other precautions:
The safety and efficacy of the veterinary medicinal product in non-target species
such as horses has not been evaluated. Adverse events have been observed in
horses including serious anaphylactic type reactions which have led to fatalities.
Revised: February 2025
AN: 03536/2024
No information is available on the safety and efficacy of this immunological veterinary
medicinal product when used with any other veterinary medicinal product. A decision
Revised: February 2025
AN: 03536/2024
to use this immunological veterinary medicinal product before or after any other
veterinary medicinal product therefore needs to be made on a case by case basis.
medicinal product when used with any other veterinary medicinal product. A decision
Revised: February 2025
AN: 03536/2024
to use this immunological veterinary medicinal product before or after any other
veterinary medicinal product therefore needs to be made on a case by case basis.
Store and transport refrigerated (2 C – 8 C).
Do not freeze.
Protect from light.
Do not freeze.
Protect from light.
Zero days.
5. IMMUNOLOGICAL PROPERTIES
Pharmacotherapeutic group: Gonadotropin releasing factor analogue, conjugated.
ATCvet code: QG03XA91.
Revised: February 2025
AN: 03536/2024
Immunisation of male pigs with Improvac induces an immune response against
endogenous gonadotrophin releasing factor (GnRF), a factor that controls testicular
function via the gonadotropic hormones LH and FSH. The active ingredient in this
immunological is a synthetically produced analogue of GnRF, which is conjugated
with an immunogenic carrier protein. The conjugate is adjuvanted to increase the
level and duration of effect.
The effects of immunisation derive from the reduction in testicular function resulting
from reduced GnRF activity. This leads to reduced production and concentration of
testosterone and other testicular steroids, including androstenone, one of the main
substances responsible for boar taint. A reduction of typical male behaviour such as
mounting and aggressiveness when mixed with non-penmates can be expected after
the second vaccination.
Boars given an initial dose of Improvac are immunologically primed but retain their
full testicular function until they receive the second dose, which induces a strong
immune response to GnRF and causes temporary immunological suppression of
testicular function. This directly controls the production of androstenone and, by
removing the inhibitory effect of testicular steroids on hepatic metabolism, indirectly
reduces levels of skatole.
This effect is apparent within one week of treatment, but it may take up to 3 weeks
for any existing concentrations of boar taint compounds to be reduced to insignificant
levels.
Immunisation of female pigs with Improvac induces an immune response against
endogenous gonadotrophin releasing factor (GnRF), a factor that controls ovarian
function via the gonadotropic hormones, LH and FSH. The active ingredient in this
immunological is a synthetically produced analogue of GnRF, which is conjugated
with an immunogenic carrier protein. The conjugate is adjuvanted to increase the
level and duration of effect.
The effects of immunisation derive from the reduction in ovarian function resulting
from reduced GnRF activity. This leads to reduced production and concentration of
oestradiol and progesterone. Prevention of typical female behaviour (standing
oestrus) and prevention of potential pregnancy can be expected from 1 to 2 weeks
post second vaccination; prevention of pregnancy is particularly relevant in situations
where fattening entire males and females are commingled.
5. IMMUNOLOGICAL PROPERTIES
Pharmacotherapeutic group: Gonadotropin releasing factor analogue, conjugated.
ATCvet code: QG03XA91.
Revised: February 2025
AN: 03536/2024
Immunisation of male pigs with Improvac induces an immune response against
endogenous gonadotrophin releasing factor (GnRF), a factor that controls testicular
function via the gonadotropic hormones LH and FSH. The active ingredient in this
immunological is a synthetically produced analogue of GnRF, which is conjugated
with an immunogenic carrier protein. The conjugate is adjuvanted to increase the
level and duration of effect.
The effects of immunisation derive from the reduction in testicular function resulting
from reduced GnRF activity. This leads to reduced production and concentration of
testosterone and other testicular steroids, including androstenone, one of the main
substances responsible for boar taint. A reduction of typical male behaviour such as
mounting and aggressiveness when mixed with non-penmates can be expected after
the second vaccination.
Boars given an initial dose of Improvac are immunologically primed but retain their
full testicular function until they receive the second dose, which induces a strong
immune response to GnRF and causes temporary immunological suppression of
testicular function. This directly controls the production of androstenone and, by
removing the inhibitory effect of testicular steroids on hepatic metabolism, indirectly
reduces levels of skatole.
This effect is apparent within one week of treatment, but it may take up to 3 weeks
for any existing concentrations of boar taint compounds to be reduced to insignificant
levels.
Immunisation of female pigs with Improvac induces an immune response against
endogenous gonadotrophin releasing factor (GnRF), a factor that controls ovarian
function via the gonadotropic hormones, LH and FSH. The active ingredient in this
immunological is a synthetically produced analogue of GnRF, which is conjugated
with an immunogenic carrier protein. The conjugate is adjuvanted to increase the
level and duration of effect.
The effects of immunisation derive from the reduction in ovarian function resulting
from reduced GnRF activity. This leads to reduced production and concentration of
oestradiol and progesterone. Prevention of typical female behaviour (standing
oestrus) and prevention of potential pregnancy can be expected from 1 to 2 weeks
post second vaccination; prevention of pregnancy is particularly relevant in situations
where fattening entire males and females are commingled.
This information is sourced from the official Summary of Product Characteristics (SPC) published by the Veterinary Medicines Directorate (VMD). It is provided for informational purposes only and does not replace professional veterinary advice. Always consult your vet before administering any medication.
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