Via PLOS Neglected Diseases: Next Steps for Ebola Vaccination: Deployment in Non-Epidemic, High-Risk Settings. Excerpt:
Due to the combination of behavioral change, active epidemiological surveillance, expanded hospital bed capacity, and other response efforts, a rapid decline in incidence restricted the number of high-transmission settings suitable for conducting vaccine trials during the 2014–2015 Ebola epidemic. Criticism of the analysis applied for the ring vaccination trial in Guinea, including imbalances in cluster sizes between trial arms and p-values that did not account for α-spending rules, has advised caution in interpreting the reported efficacy.
Prior to widespread use of the vaccine, further Phase II and III trials have been advocated. However, an epidemic of similar magnitude that could yield meaningful statistical evidence will hopefully be averted by lessons learned as well as the Ebola vaccines that were not available when the recent outbreak took hold.
Additionally, pooling evidence from a series of smaller clinical trials raises challenges, such as between-study heterogeneity in sample size, risk of exposure, and magnitude of effect.
Extraordinary scientific and humanitarian momentum was garnered during the 2014–2015 Ebola outbreak. Routine vaccination of health care workers in non-epidemic but high-risk settings could be an effective approach for sustaining this momentum. We recognize that the approach includes challenges, such as possible inter-epidemic waning of protection, a large population of health care workers who are not nurses, midwives, or physicians, and poor coverage among health care workers in more rural areas or regions less accessible due to political unrest.
In addition, criticism of the ring vaccination trial conducted in Guinea has prompted uncertainty regarding the accuracy of the estimated efficacy. Nonetheless, examining proactive vaccination strategies for Ebola prevention and response is critical to advancing development of vaccine production and administration technologies that could be instrumental to mitigating future Ebola outbreaks.