Quantifying the impact of mass vaccination programmes on notified cases in the Netherlands

Abstract

Vaccination programmes are considered a main contributor to the decline of infectious diseases over the 20th century. In recent years, the national vaccination coverage in the Netherlands has been declining, highlighting the need for continuous monitoring and evaluation of vaccination programmes. Our aim was to quantify the impact of long-standing vaccination programmes on notified cases in the Netherlands. We collected and digitised previously unavailable monthly case notifications of diphtheria, poliomyelitis, mumps and rubella in the Netherlands over the period 1919-2015. Poisson regression models accounting for seasonality, multi-year cycles, secular trends and auto-correlation were fit to pre-vaccination periods. Cases averted were calculated as the difference between observed and expected cases based on model projections. In the first 13 years of mass vaccinations, case notifications declined rapidly with 82.4% (95% credible interval (CI): 74.9-87.6) of notified cases of diphtheria averted, 92.9% (95% CI 85.0-97.2) cases of poliomyelitis, and 79.1% (95% CI 67.1-87.4) cases of mumps. Vaccination of 11-year-old girls against rubella averted 49.9% (95% CI 9.3-73.5) of cases, while universal vaccination averted 68.1% (95% CI 19.4-87.3) of cases. These findings show that vaccination programmes have contributed substantially to the reduction of infectious diseases in the Netherlands.

Keywords: Immunisation (vaccination); infectious disease epidemiology; public health; vaccine-preventable diseases.

Fig. 1.

Notified monthly cases for (a) diphtheria, (b) poliomyelitis, (c) mumps and (d) rubella, the Netherlands, 1919–2015. Notified cases are shown in black, grey areas represent periods of missing data. Dashed line indicates vaccination coverage and represents the coverage at 11 months of age for diphtheria and poliomyelitis (the primary series and first booster) and at 14 months of age for mumps. For rubella, the dashed line shows the coverage at 11 years of age up to 1977 and the coverage at 14 months of age thereafter; no vaccination data is available for cohorts born prior to 1970 and for the cohorts 1978–1984.

Fig. 2.

Notified monthly cases, model fits and counterfactual for (a) diphtheria, (b) poliomyelitis, (c) mumps, (d) rubella restricted vaccination programme of 11-year-old girls and (e) rubella extended vaccination programme of both boys and girls at 14 months and 9 years of age, the Netherlands. Observed notified cases are shown in black, median model fit is represented by the grey dashed line, and 95% credible interval in grey shaded area; vertical solid lines indicate the start of mass vaccination. Extrapolated model results for pre-vaccination period into the vaccination period are indicated by grey dashed line with 95% credible interval.