Dynamic Features of Herd Immunity: Similarities in Age-Specific Anti-Measles Seroprevalence Data between Two Countries of Different Epidemiological History.

Katalin Böröcz,Ákos Markovics,Péter Németh,Ines Drenjančević,Tímea Berki,Senka Samardžić

doi:10.3390/jcm11041145

Abstract

(1) Background: Measles immunization gap(s) raise the concern of potential outbreaks. Both Croatia and Hungary are situated in the vicinity of measles-endemic countries. Potentially compromised immunization activities due to the COVID-19 surge is a ground for concern. Our aim was to compare age-stratified seroprevalence results in the cross-border region. (2) Methods: Anti-MMR specific antibody levels (IgG) of 950 anonymous Croatian samples were compared with previous Hungarian results (n > 3500 samples), and former Croatian seroprevalence data (n = 1205). Seropositivity ratios were determined using our self-developed anti-MMR indirect ELISA (Euroimmun IgG ELISA kits were used as control). (3) Results: Measured seropositivity ratios of the Croatian samples were largely overlapping with our earlier published Hungarian data (the lowest seropositivity ratios were measured among individuals of 34–43 years of age with 78% of seropositivity) and are in accordance with earlier published data of Croatian researchers. (4) Conclusion: Although the epidemiological histories of the two countries are different, analogies in age-specific measles susceptibility have been discovered. We suggest that besides the potential coincidence in vaccination ineffectiveness, the inherent biological dynamics of vaccination-based humoral protection might have also contributed to the experienced similarities. Our findings may also serve as a lesson regarding the current anti-COVID-19 vaccination strategy.

Highlights

The recently measured and -presented seropositivity ratios (Figure 1, Supplementary Table S4) of the Croatian samples are in accordance with earlier published
Hungarian data: the lowest seropositivity ratios were measured among individuals of
In the two countries of our comparison (Hungary and Croatia) different vaccination schedules had been used, the potentially susceptible clusters are largely overlapping. In connection with this phenomenon—and based on our large-scale seroepidemiological measurements, we established a hypothetical timeline that depicts the temporal evolution of immunological protection, in the case of vaccine-preventable diseases (Figure 2)

Summary

Introduction

In Hungary, the MMR vaccine has been mandatory since 1969, with the current vaccine coverage estimated at 99% (WHO). Small-scale outbreaks (2017—the outbreak linked to the region of Makó and Szeged [7]) confirm that certain measles vaccines—applied during the early phases of the Hungarian vaccination history—failed to elicit the desired immunological response. The resulting immunization gap(s) raise the concern of potential further outbreaks [3,8]. Taking in consideration the risk of being in the geographical vicinity of measles-endemic country(ies), aggravated by the hazard of suspended immunization activities due to the COVID-19 surge

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Discussion

Conclusion