The Standing Vaccination Committee (Stiko) recommends that all healthy pregnant women from the fourth month on, all persons aged 60 and over, and the chronically ill have themselves vaccinated. The diseases through which higher risk is made present due to the seasonal influenza include: cardiovascular diseases, liver or kidney disease, respiratory diseases (including asthma) metabolic diseases such as diabetes, chronic neurological disorders such as MS, congenital and acquired immunodeficiencies such as HIV infection. The vaccination should, according to Stiko, best be provided before the influenza season starts in October or November, as it takes some two weeks before the body has fully built up its protection.
Traditional versus modern vaccination technology
In traditional chicken egg-based vaccine production, mixtures (“reassortants”) of a strongly growing and a newly recommended virus strain are used, otherwise the yield would not be sufficient. By contrast, with vero cell technology the natural virus is used: the original seasonal influenza virus with all external and internal viral proteins of the naturally occurring virus. “Experience shows that good reassortants with its respective growth characteristics cannot be prepared with all the recommended influenza virus strains. As a result vaccine shortages may occur. “Reassortants might sometimes not fully match immunologically, therefore a poorer immune response in humans is the consequence”, says Univ. Professor Herwig Kollaritsch (head of the Epidemiology Unit and Travel Medicine at the Institute of Specific Prophylaxes and Tropical Medicine, MedUni Vienna).
His conclusion: “Both pandemics and seasonal influenza epidemics require fast, reliable provision of vaccines and well-tolerated vaccines with high immunogenicity and cross-protection also against mutated strains. The conventional vaccine production with chicken eggs has often not stood up against these demands”.
New ways in dispute
HPAI (highly pathogenic avian influenza) virus such as H5N1 are in this context particularly problematic. “Infected poultry dies at a rate of 100%, which means no hens and no eggs, and consequently no possibility of conventional vaccine production”, warns Kollaritsch. Therefore there exists potential space for new technologies. “With vero cell technology the viruses are made to multiply within a continuous mammalian cell line, which ensures a high yield of virus”. The utilised cell line was derived in the 1960s from kidney cells of the green meerkat, an African primate species. Because it is a closed production system, in contrast to the production mode involving chicken eggs the use of antibiotics is able to be dispensed with.
The main advantages of the new technology
- In vero cell culture-produced vaccines, there are no egg ingredients included.
- Naturally occurring viruses are used, whereby the virus material contains its natural composition in the vaccine.
- Thanks to vero cell technology, the period between the start of production of a vaccine and delivery has been reduced from about 22 weeks to just twelve weeks.
Currently a H5N1 vaccine has already been taken for approval: a vaccine which is produced using modern vero cell technology and is highly effective and well tolerated.
Scottish study on the vaccination program against H1N1
A Scottish Cohort study at the University of Edinburgh under the direction of Prof. Alex Simpson, which was published in September 2012 in the journal The Lancet, examined the effect of influenza vaccination on the population there. Between 21 October 2009 and 31 January 2010 about 15% (38,296 people) of those ill with influenza had been vaccinated and 85% (208,882) were not vaccinated. Of the unvaccinated individuals, 5,207 had to be admitted to the emergency rooms of a hospital and 597 died. Among the vaccinated population 924 hospitalisations and 71 deaths occurred. The effectiveness of the H1N1 vaccine for the prevention of emergency hospital admissions was 19.5%. The study showed that through the ‘flu vaccine 77% of laboratory-confirmed influenza infections were prevented during the pandemic 2009/2010 in Scotland.
Influenza vaccination critically considered
A recent meta-analysis from the University of Minnesota (UM), published in the journal The Lancet, has however pointed out that those older than 65 years of age do not so strongly benefit as has been peddled until now. Study leader Michael Osterholm of the Centre for Research on Infectious Diseases at the UM analysed 5,707 articles which were published between 1967 and February 2011, and 31 studies (17 randomised and 14 observational studies). The study examined trivalent non-living vaccinations (inactivated influenza vaccine: TIV) and attenuated live vaccines (live attenuated influenza vaccine: LAIV). “We found that the currently used influenza vaccines when compared to other routinely used vaccines offer a considerably lower level of protection”.
He adds that while the currently available vaccine plays some role in reducing the death rate, the current flu vaccine simulates protection and prevents that actually effective vaccines or ‘flu protection measures might be developed. Nonetheless, Osterholm presents the view that a ‘flu vaccine across all age groups should show an efficiency of 85-95%. “The best effect of the vaccine is in healthy adolescents and adults”, says virologist Univ. Prof Terese Popov-Kraupp of MedUni Vienna. “In the best case situation, 70-80% of the infections are able to be prevented”.
Drawing correct conclusions
“The most important thing when assessing a study on the efficacy of influenza vaccines is the defined endpoint of the study”, says Redlberger. In a study on the efficacy of influenza vaccination, one has to compare the cases of laboratory-confirmed influenza in the vaccinated and in the unvaccinated groups. It is pointless, in contrast, to assess the efficacy of influenza vaccination based on the number of ‘flu infections or even doctor’s visits, since the flu vaccine only prevents influenza as an illness, but not a ‘flu viral infection or a doctor visit due to various other causes.