No 38 - 2017

Influenza vaccination 2017/2018

October 1 marks the beginning of the 2017/2018 influenza season and therefore also the launch of the free influenza vaccination offer to select population groups.

The 2016/2017 influenza season was characterised by a considerably increased number of admissions compared with previous seasons. A total of 2,940 patients with laboratory-confirmed influenza were admitted to hospital. This was the highest number of admitted patients recorded since 2010/11, when monitoring was introduced. A total of 254 patients received intensive care, which was, nevertheless, fewer than in the preceding season. Based on data on excess mortality, it was assessed that approx. 837 deaths were associated with influenza. This was slightly fewer than in the preceding season when approx. 1,000 persons died due to influenza.

The influenza vaccine used in the 2016/2017 season provided only limited protection against influenza infection, particularly so for influenza A (H3N2). Nevertheless, influenza vaccination remains the best available protection against influenza infection for elderly people aged ≥65 years or above, and for other risk groups. In the 2016/2017 influenza season, the vaccination coverage among elderly people aged ≥65 years was 47%, which is slightly higher than in the preceding years, but nevertheless far from the 75% vaccination coverage recommended by the WHO. As usual, the upcoming season’s vaccine contains antigens from three different influenza viruses, including a new influenza virus.

Free influenza vaccination

In accordance with Executive Order of 29 August 2017 on free influenza vaccination to select population groups, the following persons residing in Denmark are entitled to free influenza vaccination:

• Persons who at the time of their vaccination have reached the age of 65 years
• Early retirement pensioners
• 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
  - other chronic diseases which, according to the physician’s assessment, pose a serious health risk in conjunction with influenza
• Severe obesity (recommended BMI > 40), upon medical assessment
• Persons with other serious diseases that, according to the doctor’s assessment, pose a serious health risk in conjunction with influenza.
• Pregnant women in their 2. or 3. trimester
• Household contacts to severely immunosuppressed patients (congenital or acquired immune deficiency) upon medical assessment

The offer of free vaccination applies in the period from 1 October 2017 to the end of the year. Nevertheless, vaccination remains free until the end of February 2018 for pregnant women who at the time of their vaccination are past the first 12 weeks of gestation, and for persons with immunodeficiency and their household contacts.

The Danish Health Authority has prepared a guideline for physicians on free influenza vaccination.

Information

This year, the Danish Health Authority runs the campaign “Time for vaccination against influenza”. The campaign informs the risk groups of influenza vaccination. Doctors and healthcare workers can find information about the campaign and this year’s vaccine at www.influenzakampagne.dk. In collaboration with the General Practitioners’ Association, posters and other material were sent to GPs, pharmacies, municipalities and leading midwives. From the website, patient information, electronic campaign elements for information screens, etc., are available for download. Via the website it is possible to order several posters and visiting cards, as needed. The campaign also has a Facebook page “Tid til vaccination mod influenza” (Danish for Time for vaccination against influenza) and includes an add campaign that will run in the media from 25 September until the end of November.

Delivery

To ensure that a sufficient number of vaccines are available, two vaccines (Influvac and Vaxigrip) from two different manufacturers were ordered this year. Both vaccines contain components of inactivated influenza virus, and they are considered equal with respect to protection against influenza. None of the vaccines contains thiomersal or adjuvant. Both vaccines may contain trace amounts of eggs/chicken protein, formaldehyde, neomycin and gentamicin. For more detailed information on the individual products and "Questions & Answers", please see the SSI website.

Influenza vaccines in the 2017/2018 season

The composition of the vaccines was based on the WHO's recommendations, and the vaccines contain antigens from three seasonal influenza viruses that are in circulation globally: The following components are included:

• A/Michigan/45/2015 (H1N1) pdm09-like virus (NEW VIRUS)
• A/Hong Kong/4801/2014 (H3N2)-like virus
• B/Brisbane/60/2008-like virus (the Victoria line)

Currently, only trivalent vaccines are used in Denmark. The WHO recommends that four-valent vaccines contain two influenza B viruses.

Children

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 followed 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 www.paediatri.dk.

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. Children aged 6 through 35 months are vaccinated using only half the vaccine dose. For correct measuring of the paediatric dose, please see the package leaflet of the vaccine in question.

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 have demonstrated 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-infected persons

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 young, healthy persons, vaccination prevents up to 70-90 % of disease cases caused by influenza virus. In elderly persons, protection against ordinary influenza illness is somewhat lower. Protection against serious complications, hospital admissions and death in the elderly reaches 60%.

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 the Executive Order on Access to and Registration etc. of Medicinal Product and Vaccination Information . If the vaccination information is not automatically recorded to the DVR via integration with the electronic patient record used, vaccinations can be registered at www.fmk-online.dk.

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)

Link to previous issues of EPI-NEWS

20 September 2017