Effectiveness of a single-dose mass dengue vaccination in Cebu, Philippines: Final results of a 5-year case-control...

In mid-2017, the Philippine Department of Health launched a vaccination program of nine- to fourteen-year-old children using CYD-TDV (Dengvaxia, Sanofi) in Cebu province. The vaccination program was discontinued after only one dose was given. Until 2020, the interim vaccine effectiveness against hospitalized virologically confirmed dengue (VCD) and dengue with warning signs was 26 % and 51 %, respectively. In this report, we assess vaccine protection through February 2023.

From 15 February 2018 to 28 February 2023, we conducted a case-control study in Cebu province. Children residing in Cebu who were eligible to participate in the dengue mass vaccination in mid-2017 and subsequently admitted to any of four participating public hospitals with suspected dengue were enrolled. A blood sample was collected for dengue RT-PCR and clinical and socio-demographic information were obtained. Children hospitalized with VCD were followed until discharge and their illness classified according to WHO 2009 criteria as dengue, dengue with warning signs and severe dengue. To estimate the level of vaccine protection, vaccination status was compared between VCD cases and neighborhood controls of the same sex and age-group.

We included 584 VCD cases and 1168 controls in the analysis. Of the 584 cases, 397 (67·8 %) presented as dengue with warning sign (DWS), 8 (1·4 %) had severe dengue, and 1 (0·2 %) died. All four dengue virus serotypes were detected, but serotype 3 was the most common (287/584 or 49·1 %). Receipt of one dose of CYD-TDV was associated with 21 % (95 % CI, -7 to 41 %; p = 0·1129) overall protection against hospitalized VCD and 31 % (95 % CI, 6 to 49 %; p < 0·0001) protection against more severe presentations of dengue (dengue with warning signs and severe dengue).

A single dose of CYD-TDV conferred extended protection against more severe presentations of dengue. The study is limited by an absence of baseline dengue serostatus of the participants prior to vaccination but a large majority in this this cohort were likely dengue seropositive.