Adult schizotypal personality characteristics and prenatal influenza in a Finnish birth cohort.

Recent evidence suggests that schizophrenia may result from a disruption of normal brain development during a critical, prenatal risk period in the 6th month of gestation. The phenotypic diagnostic manifestation of a basic genetic-neurodevelopmental disorder may consist of characteristics approximated by the DSM-IV diagnosis of "schizotypal personality disorder" (SPD). We identified male conscripts in Finland who, as fetuses, were exposed to the 1969 Hong Kong Influenza epidemic, along with a group of controls born during a relatively low year (1971) for infectious epidemics. It was hypothesized that among fetuses exposed to the influenza epidemic in their 6th month of gestation, we would observe an increased frequency of elevated (upper quartile) scores on a schizotypal personality characteristics (SPC) scale as compared to controls. A significantly higher proportion of the 6th month index exposed subjects (39%) had "elevated" SPC scale scores as compared to their controls (26%) (p<0.003). Further analyses revealed that these differences were accounted for by those exposed to the influenza epidemic in week 23 (51% vs. 24%) of the 6th month (p<0.005). Exploratory analyses for the other months did not reveal any significant differences. Implications and limitations of the week 23 findings are discussed.

Comparison of two vaccination programmes in preventing influenza-related hospitalization among the elderly during two consecutive seasons.

The protective effect of influenza vaccine against influenza related hospitalization is well established at an individual level, but the effect of vaccination programme at the population level is unknown. In this study we compared a risk disease-based free-of-charge influenza vaccination programme in preventing hospitalizations due to influenza or pneumonia and cardiovascular diseases during 2 consecutive influenza seasons 1992/93 and 1993/94 in 43 municipalities in northern Finland. Vaccinations were carried out and reported by local staff in health centres. Data of hospital treatment periods were obtained from the National Hospital Discharge Register. During the influenza seasons the number of hospitalizations due to cardiovascular diseases and influenza/pneumonia increased by 13%. In the 1993/1994 season the increase in the study area with the risk disease-based vaccination programme was 22 per 1000 persons (95% CI 19-24), and with an age-based programme 3.3 per 1000 persons (95% CI 2.5-4.0), while the increase in the 1992/1993 season in both areas was 3-4 per 1000. The excess of hospitalization related to influenza epidemics is mostly due to cardiovascular diseases and varies from y to y, as do the benefits gained by vaccination.

Influence of antigenic drift on the intensity of influenza outbreaks: upper respiratory tract infections of military conscripts in Finland.

A total of 102,600 upper respiratory infections (URI) were recorded among young military conscripts in the Finnish Defence Forces during the study period from October 1991 to March 1994. This period covered three outbreaks caused by H3N2-subtype influenza A virus and one outbreak of influenza B. During the 1991/92 outbreak caused by A/Beijing/353/89-like virus, the calculated influenza A incidence was 2,206/10,000 men. During the 1992/93 outbreak when influenza B was the predominant virus, a new drift variant of influenza A that belonged to the lineage of A/Beijing/32/92-like and A/Shangdong/9/93-like viruses circulated but the incidence of influenza A was not more than 1,044/10,000. A higher incidence, 2,810/10,000, was recorded during the 1993/94 outbreak, when the circulating virus was similar to the 1992/93 virus antigenically and with regard to haemagglutinin and neuraminidase (NA) gene sequences. Crossreactive haemagglutination-inhibition antibodies induced in 1991/92 probably were sufficient to restrict the epidemic activity in 1992/93 but no longer in 1993/94. Furthermore, during the 1991/92 outbreak, some of the A/Beijing/353/89-like viruses already had shared the NA sequence markers characteristic of the viruses in 1992/93 and 1993/94, which may also have strengthened protection in 1992/93.

Influenza vaccination of dialysis patients: cross-reactivity of induced haemagglutination-inhibiting antibodies to H3N2 subtype antigenic variants is comparable with the response of naturally infected young healthy adults.

BACKGROUND: Annual influenza vaccination is recommended for patients with chronic renal failure, although vaccination responses in haemodialysis (HD) patients may be suboptimal. Typically, the seroreactivity has been analysed against the vaccine virus or the corresponding year's epidemic virus. No studies analysing cross-reactivity against subsequent years' viruses have been presented. METHODS: Twenty-three chronic HD patients and 26 cardiac patients were, in autumn 1995, vaccinated with a trivalent influenza vaccine. The cross-reacting haemagglutination-inhibiting antibodies to five consecutive years' (the last season 1999-2000) drift variants of H3N2 subtype influenza A virus were measured and compared with those of vaccinated cardiac patients and with those of 26 healthy military conscripts who suffered a serologically confirmed influenza A infection in the season 1995-1996. RESULTS: The influenza vaccination in HD patients resulted in comparable cross-reacting antibodies to the antibodies induced both by vaccination in cardiac patients and by natural infection in military conscripts. After a steady decline, the cross-reactivity to the latest epidemic virus improved in all the groups. This may be due to two reverted amino acid changes in the HA1 domain of the virus haemagglutinin. CONCLUSIONS: Influenza vaccination in HD patients is as effective as the vaccination of cardiac patients with normal kidney function. The cross-reactivity of vaccination-induced antibodies is even as good as that of antibodies induced by natural infection of young healthy males. Additionally, vaccination seems to prime the individual beneficially against subsequent years' influenza viruses.