No 39 - 2018

Influenza vaccination 2018/2019

Influenza vaccination 2018/2019

October 1 marks the beginning of the 2018/2019 influenza season and therefore also the launch of the free influenza vaccination offer to select population groups.

The 2017/2018 influenza season was prolonged and characterised by a very high influenza occurrence dominated by influenza B of the Yamagata line. The high occurrence was reflected in a high number of admitted patients and a substantial excess mortality. It was unusual for a season dominated by influenza B to cause so heavy a disease burden, EPI-NEWS 23-24/18.

The majority of the patients who were admitted with influenza belonged to risk groups, but had not been vaccinated. Despite the fact that the circulating influenza B virus and the type of virus given in the 3-valent vaccine did not match, the vaccine’s effectiveness against influenza B was, nevertheless, calculated to approx. 30%, which is likely owed to cross-protection. The vaccine also provided fairly good protection against influenza A H1N1, which was also in circulation.

Influenza vaccination is the best prevention we have against influenza infection in risk groups, including elderly people aged ≥65 years. Vaccination not only reduces the risk of infection with influenza, it also reduces the risk of developing more serious conditions, of admission to hospital and of death due to influenza, if you become infected even though you have received vaccination. In the 2017/2018 influenza season, the vaccination coverage among elderly people aged ≥65 years was approximately 50%, which is higher than in the preceding years. Nevertheless, it was far below the 75% vaccination coverage recommended by the WHO.

For the upcoming 2018/2019 season, the SSI has been able to procure a 3-valent as well as a 4-valent influenza vaccine. The 3-valent vaccine protects against two influenza A viruses and one influenza B virus. The 4-valent vaccine also protects against one additional influenza B virus.

The 4-valent influenza vaccine has been reserved for special risk groups (see below).

Free influenza vaccination

In accordance with Executive Order of 18 August 2018 on free influenza vaccination to select population groups, the following persons residing in Denmark are entitled to free influenza vaccination:

  1. Persons who at the time of their vaccination have reached the age of 65 years
  2. Early retirement pensioners
  3. Chronically ill persons who suffer from the following conditions, upon medical assessment:
    - Chronic pulmonary conditions
    - Cardiovascular diseases (barring high blood pressure with no concurrent conditions)
    - Diabetes 1 or 2
    - Congenital or acquired immunodeficiency
    - Patients whose respiration is affected due to muscular weakness
    - Chronic liver or kidney failure
    - Persons with other chronic diseases which, according to the physician’s assessment, pose a serious health risk in conjunction with influenza
  4. Severe obesity (recommended BMI > 40), upon medical assessment
  5. Persons with other serious diseases that, according to the doctor’s assessment, pose a serious health risk in conjunction with influenza
  6. Pregnant women in their 2nd or 3rd trimester
  7. Household contacts to severely immunosuppressed patients (congenital or acquired immune deficiency) upon medical assessment.

Vaccination with the 4-valent vaccine may be offered to pregnant women in their second or third trimesters and to chronically ill or severely obese people and people with other serious conditions who have not yet turned 60 years old. Additionally, it will be possible to give approx. 10% of the available 4-valent vaccines to a small group of particularly vulnerable elderly people ≥ 60 upon specific medical assessment.

If the number of 4-valent vaccines is insufficient, the above-mentioned patients are offered vaccination with the 3-valent influenza vaccine instead.

The offer of free vaccination applies in the period from 1 October 2018 to the end of the year. Nevertheless, vaccination remains free until the end of February 2019 for pregnant women who are past the first 12 weeks of gestation at the time of their vaccination, and for persons with immunodeficiency and their household contacts.

Also see Memo on free influenza vaccination and the Danish Health Authority’s information on the use of the 3- and 4-valent influenza vaccine.

Information from the Danish Health Authority

This year, the Danish Health Authority once again runs the campaign “Time for vaccination against influenza”. The campaign informs the risk groups about influenza vaccination. Doctors and healthcare workers can find information about the campaign and about this year’s vaccine at Here, you may also download patient information, electronic campaign elements for info. screens, etc. Furthermore, printed posters and business cards will be sent out to GPs, pharmacies, municipalities and leading midwives. Via the website it is possible to order several posters and visiting cards, as needed. The campaign also has a citizen-targeted Facebook page “Tid til vaccination mod influenza” (Danish for Time for vaccination against influenza) which includes an ad campaign that will run in the media while the free vaccination offer is made.

Influenza vaccines in the 2018/2019 season

This year, three vaccines were procured (Influvac, Vaxigrip and VaxigripTetra) from two different manufacturers. The composition of the vaccines was based on the WHO's recommendations, and the vaccines contain antigens from three and four seasonal influenza viruses, respectively, that are in circulation globally. All of the vaccines contain components of inactivated influenza virus. Influvac and Vaxigrip protect against two types of influenza A virus and one type of influenza B virus that the WHO assesses to be the most likely to circulate in the upcoming influenza season. In addition to the above-mentioned types of influenza, VaxigripTetra protects against one more type of influenza B virus. The two 3-valent vaccines are considered to provide equal influenza protection. The 4-valent vaccine will provide a broader protection against influenza B, but it is unlikely that influenza B Yamagata will be circulating at the same level as in the previous season, as many people will already have become immune, why it will be harder for the virus to spread in the upcoming season. None of the vaccines contain thiomersal or adjuvant. All three vaccines may contain trace amounts of eggs/chicken protein, formaldehyde, neomycin and gentamicin.

The composition of the 3-valent vaccines is as follows:

  • A/Michigan/45/2015 (H1N1) pdm09-like virus
  • A/Singapore/INFIMH-16_0019/2016 (H3N2)-like virus (NEW VIRUS)
  • B/Colorado/06/2017-like virus (the Victoria line) (NEW VIRUS)

Additionally, the 4-valent virus contains:

  • B/Phuket/3073/2013-like virus (the Yamagata line)

For more detailed information on the individual products and "Questions & Answers", please see the SSI website.


Children above the age of 6 months who are at risk of running a serious influenza course should be vaccinated. In the majority of cases, such children are monitored by a paediatric clinic, but they may also receive free vaccination at a specialist or at a vaccination clinic. A guideline from the Danish Paediatric Society is available (in Danish) at

Children aged from 6 months through 8 years who have not previously been vaccinated against influenza should receive two vaccinations at a minimum interval of 4 weeks. For both the 3-valent and the 4-valent vaccines, the same dose should be given to children and adults. Giving the same dose to children and adults is a change from previously, when it was recommended to give children aged 6-35 months of age half the adult dose.

It may be relevant to vaccinate household contacts and other persons who come into close contact with children belonging to the risk groups, including children below 6 months of age who cannot be vaccinated.

Pregnancy and breast-feeding

Pregnant women are at increased risk of suffering serious complications from influenza infection compared with non-pregnant women, and this is particularly evident for influenza A(H1N1) pdm09, which has been in circulation since 2009.

The Danish Health Authority therefore recommends influenza vaccination of all pregnant women in their second or third trimester. Pregnant women in their first trimester are also vaccinated, provided that they belong to a risk group.

Many years of experience with vaccination of pregnant women globally show that influenza vaccination during pregnancy is safe for the child and not associated with an increased risk of adverse reactions for the pregnant woman. Influenza vaccination of pregnant women may also protect the child in the first months of life as antibodies are transferred from mother to child. The influenza vaccine may also be given during the breastfeeding period.

HIV infectees

Like all other immunocompromised persons, HIV-infected persons are at an increased risk of running a serious influenza course, and all doctors are therefore encouraged to offer free influenza vaccination to their HIV-infected patients.

Degree of protection

Immunity achieved through vaccination with inactivated influenza virus is generally effective 2-3 weeks after vaccination, and the effect generally lasts 6-12 months. The degree of protection depends mainly on the correlation between the type of virus in circulation and the virus strains in the vaccine. In younger, healthy persons, vaccination on average prevents 60% of influenza cases. In the elderly, protection against clinical influenza is somewhat lower, but even so, influenza vaccination may protect against serious complications, hospital admission and death.

Adverse reactions and contraindications

Fever, malaise, rigours and tiredness are common vaccination reactions. They typically recede after 1-2 days. The inactivated influenza vaccines do not cause influenza illness.

Persons who are hypersensitive to chicken eggs/chicken protein or other vaccine ingredients and who previously experienced a reaction resembling an anaphylactic shock should not be vaccinated.

Allergy to formaldehyde will most frequently manifest itself as contact dermatitis in which case patch tests may be positive. However, this does not constitute a contraindication. To avoid such reaction, the vaccine may be administered intramuscularly.

Neuraminidase inhibitors can be used for treatment and in some cases also for prevention following specific exposure in persons who cannot be vaccinated due to contraindications.

Registration of vaccinations

All influenza vaccinations shall be registered in the Danish Vaccination Register (DVR) in accordance with Executive Order on Access to and Registration etc. of Medicinal Product and Vaccination Information. If the vaccination information is not automatically reported to the DVR via integration with the electronic patient record used, vaccinations can be registered at

Influenza surveillance

Statens Serum Institut's influenza surveillance will be in place as from Week 40. Data from the influenza surveillance will be updated on the SSI website weekly, and news will be published continuously as the influenza situation changes.

(I.G. Helmuth, L.K. Knudsen, T.G. Krause, Department of Infectious Disease Epidemiology and Prevention, A.K. Devantier, B. Søborg, Unit for Evidence, Education and Emergency Services, Danish Health Authority)