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. 2020 Apr 27;15(4):e0230406.
doi: 10.1371/journal.pone.0230406. eCollection 2020.

Impact of prophylactic vaccination strategies on Ebola virus transmission: A modeling analysis

Ravi Potluri  1 , Amit Kumar  2 , Vikalp Maheshwari  2 , Charlie Smith  3 , Valerie Oriol Mathieu  4 , Kerstin Luhn  4 , Benoit Callendret  4 , Hitesh Bhandari  2
Affiliations

Impact of prophylactic vaccination strategies on Ebola virus transmission: A modeling analysis

Ravi Potluri et al. PLoS One. .

Abstract

Ebola epidemics constitute serious public health emergencies. Multiple vaccines are under development to prevent these epidemics and avoid the associated morbidity and mortality. Assessing the potential impact of these vaccines on morbidity and mortality of Ebola is essential for devising prevention strategies. A mean-field compartmental stochastic model was developed for this purpose and validated by simulating the 2014 Sierra Leone epidemic. We assessed the impacts of prophylactic vaccination of healthcare workers (HCW) both alone and in combination with the vaccination of the general population (entire susceptible population other than HCW). The model simulated 8,706 (95% confidence intervals [CI]: 478-21,942) cases and 3,575 (95%CI: 179-9,031) deaths in Sierra Leone, in line with WHO-reported statistics for the 2014 epidemic (8,704 cases and 3,587 deaths). Relative to this base case, the model then estimated that prophylactic vaccination of only 10% of HCW will avert 12% (95% CI: 6%-14%) of overall cases and deaths, while vaccination of 30% of HCW will avert 34% of overall cases (95% CI: 30%-64%) and deaths (95% CI: 30%-65%). Prophylactic vaccination of 1% and 5% of the general population in addition to vaccinating 30% of HCW was estimated to result in reduction in cases by 44% (95% CI: 39%-61%) and 72% (95% CI: 68%-84%) respectively, and deaths by 45% (95% CI: 40%-61%) and 74% (95% CI: 70%-85%) respectively. Prophylactic vaccination of even small proportions of HCW is estimated to significantly reduce incidence of Ebola and associated mortality. The effect is greatly enhanced by the additional vaccination even of small percentages of the general population. These findings could be used to inform the planning of prevention strategies.

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Conflict of interest statement

The study was commissioned and funded by Janssen Vaccines & Prevention of Johnson and Johnson. At the time of conducting the study, Charlie Smith, Valerie Oriol Mathieu, Kerstin Luhn and Benoit Callendret were full-time employees and potential stockholders of Janssen Pharmaceuticals Inc. or its affiliates, and Ravi Potluri, Amit Kumar, Vikalp Maheshwari and Hitesh Bhandari were full-time employees of SmartAnalyst Inc. or its affiliate. This does not alter our adherence to PLOS ONE policies on sharing data and materials. There are no patents, products in development or marketed products to declare.

Figures

Fig 1
Fig 1. Expanded SEIR framework-based model differentiating between HCW and the general population, permitting movement between populations based on infection status, and accommodating vaccination.
Abbreviations: S, susceptible population; GP, general population; HCW, healthcare workers; General population, total population minus HCW; NP, not protected; P, protected.
Fig 2
Fig 2. Reported Ebola cases for the 2014 Sierra Leone epidemic–among overall population (weekly cases) and in HCW (monthly cases).
Abbreviation: HCW, Healthcare workers; WHO, World Health Organization. Data for the figures were obtained from the WHO [31] and the study by Fang and colleagues [29].
Fig 3
Fig 3. Comparison of the output of the base case model (without vaccination) with published data.
A, Cumulative Ebola cases. B, Cumulative Ebola mortality. C, Comparison of cumulative Ebola cases reported by the WHO with model output. D, Comparison of cumulative Ebola-related mortality reported by the WHO with model output. E, Cumulative Ebola cases among HCW. F, Comparison of cumulative HCW Ebola cases reported by Fang and colleagues with model output. Abbreviation: HCW, Healthcare Workers; WHO, World Health Organization.
Fig 4
Fig 4. Impact of prophylactic vaccination of different proportions of HCW on cumulative incidence and mortality associated with Ebola virus disease.
Abbreviations: HCW, health care worker; H10, vaccination of 10% of all HCW; H30, vaccination of 30% of all HCW.
Fig 5
Fig 5. Impact of prophylactic vaccination of different proportions of the general population, in addition to vaccination of 30% of HCW, on cumulative incidence and mortality associated with Ebola virus disease.
Abbreviations: G, general population; HCW, health care worker; H30, vaccination of 30% of all HCW; H30-G1, vaccination of 30% of all HCW plus 1% of the general population; H30-G5, vaccination of 30% of all HCW plus 5% of the general population.
Fig 6
Fig 6. Incremental benefit of prophylactic vaccination of the general population as a function of the vaccination coverage.
Abbreviations: HCW, health care worker; H30, vaccination of 30% of all HCW; H30-Gx, vaccination of 30% of all HCW plus x% of the general population.
Fig 7
Fig 7. Impact of reactive mass vaccination on cumulative incidence and mortality associated with Ebola virus disease, compared with H30-G5 prophylactic vaccination strategy.
Vaccine profile assumed for mass vaccination: Time to onset of protection: 7 days, duration of protection: 180 days, efficacy: 100%. Daily rate at which vaccination is carried out: 0.1% (general population) and 5% (HCW). Abbreviations: HCW, health care worker; H30-G5, vaccination of 30% of all HCW plus 5% of the general population.
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