Population preventable fraction of total multiple sclerosis risk associated with non-specific effects of vaccinations against hepatitis B virus and influenza A and B viruses in a middle eastern country.

BACKGROUND

This study aimed to quantify the population attributable (or prevented) fraction (PAR or PPF) of common risk factors for multiple sclerosis (MS) including family history of MS and vaccine uptake against influenza A and B viruses and hepatitis B virus.

METHODS

Confirmed MS cases and MS-free controls pair-matched on age (± 5 years), sex and nativity with cases were enrolled. Data were collected through face-to-face interviews both from the cases and controls. An unconditional multivariable logistic regression model was used to analyze the data by including matching factors i.e., age, sex, and nativity as confounders and MS family history and vaccine uptake against influenza viruses and hepatitis B virus as exposures. The adjusted odds ratios and their 95% confidence intervals (CI) were used to compute PAR for family history of MS and PPFs for vaccine uptake against HBV and influenza virus along with their respective 95% CIs.

RESULTS

A total of 110 MS cases, and their 110 pair-matched controls were enrolled. The PAF for family history of MS revealed that 22% of MS risk in the population is contributed by family history of MS (PAF = 0.22; 95% CI: 0.10-0.32). The PPFs for vaccination uptake against influenza viruses and/or hepatitis B virus were associated with a significant nonspecific protection against MS risk by 20% (PPF = 0.20; 95% CI: 0.004-0.43) or 30% (PPF = 0.30; 95% CI: 0.03-0.65) respectively. Moreover, the computed joint PPF for vaccination uptake against influenza viruses and hepatitis B virus showed a significantly increased 44% non-specific protection against MS risk (PPF = 0.44; 95% CI: 0.03-0.80).

CONCLUSIONS

Familial history of MS is associated with 22% population attributable fraction for MS risk, whereas vaccine uptake against influenza viruses or hepatitis B virus conferred a nonspecific protection with population prevented fractions of 20% and 30% respectively suggesting a substantial potential for public health interventions to minimize MS risk in this and other similar settings.