Key result
Oral polio vaccine titers decline significantly as distribution moves from central to peripheral supply chains.
Why the study?
Circulating vaccine-derived polioviruses persist in the Democratic Republic of the Congo due to factors including cold chain quality, which may reduce vaccine effectiveness.
Does distribution through the health system cold chain reduce the viral titer and viability of oral poliovirus vaccines in Kinshasa?
Cross-Sectional (n=53)
Yes
Does distribution through the health system cold chain reduce the viral titer and viability of oral poliovirus vaccines in Kinshasa?
p-value: p=0.008
Oral poliovirus vaccine viral titers decline significantly from central to peripheral distribution levels, highlighting vulnerabilities in the cold chain that could compromise immunization efforts.
May signal cold chain vulnerabilities in peripheral Kinshasa; hypothesis-generating for impacts on polio vaccine potency.
Background: Poliomyelitis is a vaccine-preventable disease, with oral poliomyelitis vaccines (OPVs) and injectable poliomyelitis vaccines. In the Democratic Republic of the Congo (DRC), circulating vaccine-derived polioviruses (VDPVs) persist due to intrinsic and extrinsic factors, including the quality of the cold chain, which may make the vaccines less effective. This study’s objective was to evaluate the cold chain’s quality of OPVs and its effect on the vaccine’s viability and potency at different levels in health systems in Kinshasa. Methods: A cross-sectional study was conducted in Kinshasa, collecting OPVs at different levels of the health pyramid. Vaccine viability was assessed by cell culture using a modified World Health Organization (WHO) protocol, and the viral titer was determined using the Karber formula. The vaccine titer was classified as “very good”, “good”, or “poor” according to the WHO standard’s viral titer. Results: A total of 53 vaccines were collected and analyzed, compressing 38 bivalent oral poliomyelitis (bOPV) vaccines and 15 novel oral poliomyelitis vaccines, type 2 (nOPV2). The viral titer ranged from log105.8 to log 107.3 and from log105.4 to log108.9 for the nOPV2 and the bOPV, respectively. Of these 53 vaccine samples, 10% of the bOPVs showed viral titers below the recommended WHO threshold (>106 CCID50/dose), 100% of the nOPV2 had viral titers within the WHO standards (>105 CCID50/dose), and a significant decline in the viral titer was observed for both types of vaccines (nOPV2 and bOPV) as the distribution progressed along the level of the health pyramid. Conclusions: This study demonstrated that the viral titer of OPV declined from central to peripheral areas in routine and campaign strategies in Kinshasa.
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Kashitu-Mujinga et al. (2025) conducted a cross-sectional in Oral Poliovirus Vaccine Viability (n=53). Distribution to peripheral health levels vs. Central level storage was evaluated on Vaccine viral titer and viability (p=0.008). The viral titer of both nOPV2 and bOPV vaccines significantly declined as they progressed from central to peripheral areas of the health pyramid (p=0.008 for bOPV differences across levels).
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