Against the new H1N1 influenza (swine influenza): vaccinate or don't vaccinate (all)? That is currently the question!

Recent publications in medical microbiology and immunology: a retrospective

A look back is done to some clinical and basic research activities recently published in medical microbiology and immunology. The review covers clinical experiences and in vitro experiments to understand the emergency, pathogenicity, epidemic spread, and vaccine-based prevention of avian and swine-origin flu. Some new developments and concepts in diagnosis, (molecular) epidemiology, and therapy of AIDS, viral hepatitis C, and herpesvirus-associated diseases are outlined. Regulation of immune system has been discussed in a special issue 2010 including some aspects of CNS affections (measles). Mycobacterial infection and its prevention by modern recombinant vaccines have reached new interest, as well as new concepts of vaccination and prophylaxis against several other bacteria. Adaptation to host niches enables immune escape (example brucella) and determines virulence (example N. meningitidis). Chlamydia pneumoniae, previously considered to trigger atherosclerosis, is hypothetically associated to Alzheimer disease, while CMV, another putative trigger of atherosclerosis, gains evidence of oncomodulation in CNS tumor diseases. In terms of globalization, exotic virus infections are increasingly imported from southern countries.

Did the pandemic have an impact on influenza vaccination attitude? A survey among health care workers

Background

Health care workers' (HCWs) influenza vaccination attitude is known to be negative. The H1N1 epidemic had started in mid 2009 and made a peak in October-November in Turkey. A national vaccination campaign began on November 2^nd, 2009. Despite the diligent efforts of the Ministry of Health and NGOs, the attitudes of the media and politicians were mostly negative. The aim of this study was to evaluate whether HCWs' vaccination attitudes improved during the pandemic and to assess the related factors.

Methods

This cross-sectional survey was carried out at the largest university hospital of the Aegean Region-Turkey. A self-administered questionnaire with 12 structured questions was applied to 807 HCWs (sample coverage 91.3%) before the onset of the vaccination programme. Their final vaccination status was tracked one week afterwards, using immunization records. Factors influencing vaccination rates were analyzed using ANOVA, t-test, chi-square test and logistic regression.

Results

Among 807 participants, 363 (45.3%) were doctors and 293 (36.6%) nurses. A total of 153 (19.0%) had been vaccinated against seasonal influenza in the 2008-2009 season. Regarding H1N1 vaccination, 143 (17.7%) were willing to be vaccinated vs. 357 (44.2%) unwilling. The number of indecisive HCWs was 307 (38.0%) one week prior to vaccination. Only 53 (11.1%) stated that they would vaccinate their children. Possible side effects (78%, n = 519) and lack of comprehensive field evaluation before marketing (77%, n = 508) were the most common reasons underlying unwillingness or hesitation.

Among the 749 staff whose vaccination status could be tracked, 228 (30.4%) actually received the H1N1 vaccine. Some of the 'decided' staff members had changed their mind one week later. Only 82 (60%) of those willing, 108 (37%) of those indecisive and 38 (12%) of those unwilling were vaccinated.

Indecisive HCWs were significantly younger (p = 0.017). Females, nurses, and HCWs working in surgical departments were more likely to reject vaccination (p < 0.05). Doctors, HCWs working in medical departments, and HCWs previously vaccinated against seasonal influenza were more likely to accept vaccination (p < 0.05). Being younger than 50 and having been vaccinated in the previous season were important predictors of attitude towards pandemic influenza vaccination.

Conclusions

Vaccination rates increased substantially in comparison to the previous influenza season. However, vaccination rates could have been even higher since hesitation to be vaccinated increased dramatically within one week (only 60% of those willing and the minority of those indecisive were finally vaccinated). We speculate that this may be connected with negative media at the time.

Limited prevalence of influenza A/H1N1v antibodies: footprints of the pandemic of 2010

BACKGROUND

The intention of our investigation was to determine the seroprevalence of H1N1v antibodies after a pandemic by the haemagglutination inhibition (HI) test. We included the serum samples of adults who had not received vaccination against H1N1v. By means of serological footprints, the spread of infection can be investigated.

MATERIALS AND METHODS

Between December 2009 and May 2010, we collected 233 serum samples from healthy people aged 1-72 years and analysed the titres of H1N1v antibodies by the use of the HI test.

RESULTS

After the pandemic, a seroprevalence of 36.9% was observed. The highest rate of seropositivity was detected in the age group of 10-19 years (60%) and the lowest rate was found in the age group of 30-39 years (22%). The seroprevalence of H1N1v antibodies in females exceeded the rate of positive men (41.5 vs. 31.8%). Almost 70% of the influenza A/H1N1v infections were passed inapparently.

Determination of serum antibodies against swine-origin influenza A virus H1N1/09 by immunofluorescence, haemagglutination inhibition, and by neutralization tests: how is the prevalence rate of protecting antibodies in humans?

In April 2009, a new variant of influenza A virus, subtype H1N1v emerged in Mexico and spread all over the world producing the H1N1 pandemic in mankind after 1918-1920 and 1978/1979. Obviously there was no herd immunity against this new virus variant. Mainly young people, but less elderly were affected and presented severe and even lethal courses of disease. Since virus-specific antibodies are commonly regarded as markers of partial or complete immunoprotection, we performed antibody determinations in serum samples obtained from people before and after the pandemic has arrived in our region (Frankfurt/M., Germany). The assays were done by indirect immunofluorescence, by neutralization test, and by a haemagglutination inhibition test (HI), which was established in a practical modification for general and easy use. Among 145 individuals, of whom serum specimens had been drawn before the onset of pandemic, 19 revealed humoral immunity, i.e. titres of H1N1v neutralizing antibodies (at least 1:64). Eleven were older than 60 years, one belonged to the age group 40-59 years, three to the age group 20-39 years, and two to the age group 15-19 years. After the onset of pandemic in Frankfurt, serum specimens drawn from n = 225 randomly selected patients of our local university hospital were investigated for antibodies against H1N1v by HI, which is generally recommended for routine check of immunity. Twenty-eight individuals revealed the protecting antibody titre of at least 1:40. The age distribution had moved to mean age groups. The results fit to the incidence of influenza A/H1N1(09) disease, as confirmed by RT-PCR in patients admitted to our hospital, peaking in the younger age groups up to 30 years (second affected group: 30-40 years). While commonly used solid-phase antibody tests (like immunofluorescence) are not suitable to diagnose passed H1N1(09) infection and acquired immunity, this can be easily done by HI. Expecting the next waves of influenza A/H1N1v infections, HI testing may avoid vaccinations under special risk of severe or hidden adverse reactions.