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  • About the monkeypox vaccine

Article

About the monkeypox vaccine

Norway has been allocated a limited number of vaccine doses for use against monkeypox. The vaccine will be prioritised for close contacts of people with monkeypox. Vaccination alone is not enough to reduce transmission, so other infection control measures will still be necessary.

Norway has been allocated a limited number of vaccine doses for use against monkeypox. The vaccine will be prioritised for close contacts of people with monkeypox. Vaccination alone is not enough to reduce transmission, so other infection control measures will still be necessary.


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Vaccines used in Norway

Globally, there is extremely limited availability of vaccines against monkeypox. The distribution to European countries is based on population figures and the vaccines are distributed fairly to the EU countries through HERA, the EU's health preparedness and response authority. Norway has been offered doses sufficient for approximately 700 people, depending on how the doses are used. This type of vaccine takes time to produce and it is unclear when more vaccine doses will be available.

In order to begin vaccination quickly, the Ministry of Health and Care Services has agreed to use vaccine doses from the existing smallpox emergency stockpile and replace them with the doses allocated by the EU.

No vaccine has been developed specifically against monkeypox. In July, a smallpox vaccine was approved for use against monkeypox in Europe. The vaccine is a third-generation smallpox vaccine and consists of live, weakened, non-replicating Vaccinia Ankara virus. This means that it is a live vaccine, but the virus has been weakened so that it can no longer divide and reproduce. Knowledge of the vaccine's effect against monkeypox is primarily based on animal studies, but it is assumed to provide protection against monkeypox in humans. It is marketed under the trade name Imvanex in Europe, Jynneos in the USA and Imvamune in Canada. The Imvanex and Jynneos vaccines will be available in Norway.

Who should be vaccinated?

There are not enough vaccines for everyone, so close contacts of people who have been diagnosed with monkeypox will be prioritised for vaccination. People who may have been exposed to the virus will be offered vaccination after specific assessment and prioritisation by a doctor (so-called post-exposure vaccination). The prioritisation is based on the risk of infection depending on the type of contact, the time that has elapsed since contact and the risk of a severe disease course. The use of the vaccines is constantly assessed by the Norwegian Institute of Public Health, and the recommendations for vaccination and prioritisation may change.

The vaccine can be offered to people who have been exposed to high-risk infection (sexual contacts and household members) in the first four days after exposure. This is to reduce the risk of developing the disease. People who are at high risk of developing a severe disease course (small children, pregnant women and people with immunodeficiency) can be offered the vaccine up to and including day 14 after exposure, in order to reduce the risk of a severe disease course.

There are no reliable figures on how many people are at high risk of exposure to infection, but a rough estimate is about 2,000-3,000 people. This means that we do not have enough vaccines to offer preventive vaccination before an infection situation occurs (pre-exposure vaccination) to everyone, although the Norwegian Institute of Public Health will assess whether this may be relevant for certain groups on an ongoing basis.

How effective are the vaccines?

There are no data available for vaccination after exposure to infection but animal studies have shown that the vaccine provides protection as early as 4 days after vaccination.

There are no human data for vaccination after exposure, but an animal study has shown that vaccination one day after exposure to the virus protects the animals both against death and the development of skin rashes. When the vaccine was given three days after exposure, a somewhat reduced protection was observed. It is therefore assumed that the vaccine can protect against disease development if it is given shortly after exposure (0-4 days). The burden of symptoms is probably reduced if the vaccine is given 5-14 days after exposure. It is not known whether the vaccine will protect against further transmission.

Vaccination will come in addition to other infection control advice. If you are exposed to high-risk transmission (sexual contacts and household members), it is recommended to avoid close contact with others and monitor whether you develop symptoms, regardless of whether you have been vaccinated or not. If you develop symptoms (fever, muscle pain, headache, swollen lymph nodes, rash) you should go into isolation and contact a doctor for an examination. The doctor will assess whether you should take a test.

These vaccines have not previously been used on a large scale against monkeypox, and it is therefore uncertain how effective they will be. The aim of vaccination will be to prevent the development of a severe disease course and to limit transmission.

How can those who are recommended to be vaccinated get the vaccine?

If the municipality's contact tracing team considers it appropriate to offer vaccination, the municipal medical officer and NIPH should be involved in the assessment. It can take up to 1 day from ordering the vaccine until it is available in the municipality. The municipality itself will decide where vaccination takes place - for example, a vaccination centre, doctor’s office or out-of-hours medical service.

How is the vaccine given?

The vaccine is placed under the skin in the upper arm and is approved as a two-dose regimen. This means that people who have not previously had a smallpox vaccine will be given two doses at least 28 days apart.

For people who have previously been vaccinated against smallpox, a single booster dose is sufficient. People with impaired immunity who have previously been vaccinated against smallpox should receive two booster doses. The second booster dose must be given no earlier than 28 days after the first dose.

When the vaccine is given after exposure, it is assumed that symptoms have not yet developed - this applies to both the first and the second dose.

As there is limited access to vaccines globally, it is being continuously assessed whether it is possible to distribute the existing doses among more people, for example, by postponing the second dose for those who are offered vaccination after having been exposed to infection for an indefinite period of time or by dividing each dose into several smaller doses. For the time being, Norway will follow the recommended dosage behind the approval of the vaccine, i.e., the two-dose regimen.

Healthcare personnel

Due to the low risk of infection and limited access to vaccine doses, it has been considered that healthcare personnel should not be offered the vaccine for the time being. Healthcare personnel who treat infected patients or have a high probability of contact with infected people can effectively protect themselves with other infection control means. In the current outbreak of monkeypox, there have been no reports of transmission to healthcare personnel while at work.

Employees in the health service who are at risk of complications from infection with the monkeypox virus, such as pregnant women and employees with immunodeficiencies, should not work with people with suspected or confirmed monkeypox.

Children

Children have a higher risk of a severe disease course than adults. If the vaccine is to be offered to children, this should be done after individual assessment by the attending doctor in consultation with NIPH. In the current outbreak of monkeypox, some children in Europe have received the vaccine after exposure (post-exposure vaccination) and no unexpected incidents have been reported.

Pregnant and breastfeeding women

There are limited data on the use of this type of vaccine among pregnant and breastfeeding women, but no harmful effects are suspected from animal studies. Pregnant women have an increased risk of a severe monkeypox disease course, and the risk is probably higher towards the end of pregnancy. Vaccination can be considered for pregnant women after a careful assessment of the risk of infection and severe disease course, weighed against a possible unknown risk when vaccinating mother and child. Breastfeeding women can be vaccinated.

Who should not be vaccinated against monkeypox?

People who have:

  • known allergy to the ingredients in the vaccine. The vaccine contains trace amounts of chicken protein, benzonase, gentamicin and ciprofloxacin and should not be used for people with a known allergy to these.
  • an acute infectious disease with fever above 38 °C
  • already had monkeypox

Side effects

The most common side effects are temporary and short-term in the form of:

  • reactions at the injection site
  • general reactions such as muscle pain, headache, nausea and lethargy
  • People with atopic eczema have an increased risk of side effects and worsening of eczema. For a complete list of known side effects, see the full product summary (SPC) which can be found by searching the Swedish Medicines Agency's website.

When the vaccine is given after exposure to infection, it can be difficult to distinguish side effects after vaccination from symptoms of monkeypox disease. People who have been exposed to infection and who have received post-exposure vaccination should follow the same advice as unvaccinated people. If symptoms consistent with monkeypox occur, a doctor should assess the symptoms and decide whether a test should be taken.

If monkeypox is detected in people who have received one or two doses of vaccine, this should be reported as vaccine failure.

Since the vaccine has been approved on a special basis, it is marked with a black triangle and subject to special monitoring in order to discover new safety information as quickly as possible. Healthcare personnel are encouraged to report any suspected side effects (including vaccine failure) via melde.no.

History

12.08.2022: Added sentence about data about effect from animal studies