Children with prior dengue virus infection had a decreased risk of being symptomatic when infected with Zika virus, according to a study published in PLoS Medicine.

In an ongoing, community-based prospective study of 3700 children between the ages of 2 and 14 years with a well-characterized history of prior dengue virus infection, researchers sought to determine the effect of prior dengue virus infection on Zika infection outcomes during the 2016 Zika epidemic in Managua, Nicaragua.

Of the 3027 children with known dengue infection histories, 743 children had experienced at least 1 prior dengue infection and 176 experienced a recent dengue infection. Prior dengue infection was defined as at least 1 inapparent or symptomatic infection since entering the study until the 2015/2016 season (from March 2015 through February 2016), and recent dengue infection was defined as an inapparent or symptomatic infection during the 2015/2016 season.

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From January 2016 through February 2017, researchers estimated that there were 1356 Zika infections, with 560 being symptomatic cases. The overall incidence of Zika infection was 14.0 symptomatic cases per 100 person-years (95% CI, 12.9-15.2). On the basis of the generalized-growth method, the effective reproduction number estimates ranged from 3.3 to 3.4, depending on the ascending wave period.

The incidence of symptomatic Zika and total Zika infections (symptomatic and inapparent) was higher in girls than in boys, and increased in direct proportion with age.

Compared with children with no prior dengue infection, children with prior dengue infection had significantly lower incidence of symptomatic Zika and a lower rate of symptomatic presentation of Zika virus infection. Multivariable models adjusted for age and sex demonstrated that both having a prior dengue infection and having a recent dengue infection were inversely associated with risk for symptomatic Zika infection. However, when adjusted for age, sex, and recent dengue infection, only prior dengue infection remained negatively associated with risk for symptomatic Zika virus infection (incidence rate ratio, 0.63; 95% CI, 0.48-0.81; P <.005) and with risk for symptomatic presentation of Zika virus infection (incidence rate ratio, 0.62; 95% CI, 0.44-0.86; P =.004).

Prior or recent dengue virus infection did not affect the rate of total Zika virus infections.

Findings from the study are limited to a pediatric population and constrained by the epidemiology of the site. Nevertheless, the “findings support the idea that prior [dengue virus] immunity might cross-protect against symptomatic Zika,” noted the researchers.

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“More research is needed to address the possible immunological mechanism(s) of cross-protection between [Zika virus] and [dengue virus] and whether [dengue virus] immunity also modulates other [Zika virus] infection outcomes such as neurological or congenital syndromes,” they concluded.

Gordon A, Gresh L, Ojeda S, et al. Prior dengue virus infection and risk of Zika: A pediatric cohort in Nicaragua. PLoS Med. 2019;16(1):e1002726.