No 38-39- 2014

Influenza vaccination 2014/2015

1 October marks the beginning of the 2014/2015 influenza season and therefore also the introduction of the free influenza vaccination offer to selected population groups.

The past influenza season was characterised by a remarkably low influenza activity in the population in general. On the other hand, a total of 108 patients were admitted with influenza at Danish intensive care units. More than 70% of the intensive care patients had an underlying condition or were 65 years old or more, and only 19% had received influenza vaccination.

This underlines the importance of increasing the influenza vaccination coverage, particularly among risk groups and persons aged 65 years and older. The WHO's objective is a 75% coverage in this age group; in 2013/2014, however, coverage in Denmark only reached 47%.

Free influenza vaccination

In accordance with Executive Order of 27 August 2014 on free influenza vaccination to selected population groups, the following persons residing in Denmark are entitled to free influenza vaccination:

• Persons who have reached the age of 65 years at the time of their vaccination 
• 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
• Severely obese persons (recommended BMI > 40) upon medical assessment
• Persons with other serious diseases- which - according to the doctor’s assessment - pose a serious health risk in conjunction with influenza.
• Pregnant women in their 2nd and 3rd trimesters
• Household contacts to severely immunosuppressed patients (congenital or acquired immunodeficiency) upon medical assessment

The offer of free vaccination applies in the period from 1 October to the end of year 2014. For pregnant women in their 2nd and 3rd trimesters and for immunosuppressed persons and their household contacts, the period is extended until the end of February 2015.

The Danish Health and Medicines Authority has prepared a guideline on free influenza vaccination for physicians. The guideline is available (in Danish language) at www.retsinformation.dk.

Further information on influenza vaccination for risk groups is available (in Danish Language) at the Danish Health and Medicines Authority's website www.beskytdigmodinfluenza.dk.

Delivery

This year two vaccines were ordered (Fluarix and Vaxigrip) from two manufacturers. Both vaccines contain components of inactivated influenza virus, and they are considered equal with respect to protection against influenza. None of the vaccines contain thiomersal or adjuvant. Both vaccines may contain trace amounts of eggs/chicken protein, formaldehyde and gentamicin. For more detailed information on the individual products and "Questions & Answers", please see www.ssi.dk.

Influenza vaccines in the 2014/2015 season

The composition of the vaccines is based on the WHO's recommendations, and the vaccines contain antigens from three seasonal influenza viruses which are in circulation globally, as was the case in the past season:

• A/California/7/2009 (H1N1)pdm09-like virus 
• A/Texas/50/2012 (H3N2)-like virus
• B/Massachusetts/2/2012-like virus (the Yamagata line)

Children

Children above the age of six months with a risk of running a serious influenza course should be vac¬cinated. In the majority of cases, such children are monitored by a paediatric clinic, but they may also receive free vaccination at a GP/specialist or at a vaccination clinic. A guideline from the Danish Paediatric Society is available for download (in Danish) at www.paediatri.dk.

Children aged from six months through eight years and who have not previously been vaccinated against influenza should receive two vaccinations at a minimum interval of four weeks. Children aged 6 through 35 months are vaccinated using only half the vaccine dose.

It may be relevant to vaccinate household contacts and other persons who come into close contact with children belonging to risk groups.

Pregnancy and breast-feeding

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

The Danish Health and Medicines Authority therefore recommends influenza vaccination of all pregnant women in their 2nd and 3rd trimesters. Pregnant women in their 1st trimester are also vaccinated, provided 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 the 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 period of breastfeeding.

Multiple sclerosis and HIV

Patients with multiple sclerosis may risk having new attacks if their disease is complicated by influenza. No increase has been observed in the risk of new attacks as a result of vaccination. Guidance concerning vaccination of HIV-infected patients is provided by the infectious diseases department where the patient attends follow-up.

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 is, in particular, dependent 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 influenza cases. 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 reactions, which 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 have previously experienced an anaphylactoid reaction should not be vaccinated. Allergy to formaldehyde will most frequently manifest itself as contact dermatitis in connection with which patch tests may be positive; this does not comprise a contraindication. To avoid such reaction, the vaccine may be administered intramuscularly.

Neuroaminidase inhibitors may be used prophylactically in persons who are unvaccinated due to contraindications and in unvaccinated contacts.

Influenza surveillance

Statens Serum Institut's influenza surveillance will be in place as from Week 40. INFLUENZA-NEWS including weekly updates on national Danish as well as international influenza incidences will start being published once the initial signs of influenza activity have been observed.
(T.G. Krause, L.K. Knudsen, Department of Infectious Disease Epidemiology)

Specimen medium for submission of specimens for influenza surveillance

The SSI takes this opportunity to inform that the swabbing kit ESwabTM from Copan is not suitable for virus cultures submitted as influenza surveillance specimens. ESwabs are suitable only for diagnostic purposes when virus RNA is detected using PCR.

As part of the national and international influenza surveillance, the International Influenza Centre at the SSI is to characterise the influenza viruses circulating in Denmark. This includes, among others, testing of viruses for antigen and genetic changes, vaccine match and resistance to antiviral agents.

These tests can only be performed if it is possible to culture virus isolates from cell culture specimens. Unfortunately, the ESwab kit is toxic to the cells used to culture influenza virus; and the chance to perform these tests is therefore foregone, along with important knowledge.

The SSI therefore requests that one of the following be used when influenza specimens are submitted to the SSI as part of the influenza surveillance: universal transport medium (UTM)/virus transport medium (VTM), phosphate-buffered saline (PBS), or simply physiological saline.

(R. Trebbien, T.K. Fischer, Microbiological Diagnostics and Virology)

Link to previous issues of EPI-NEWS

24 September 2014