WE may still remember vividly the great scare we all had during 2015 when there was an outbreak of Ebola in West Africa and a distinct fear that the virus could be carried to us by an infected but still asymptomatic passenger on a plane.

As the risk of death (mortality) from ebola was stated to be around 80 to 90 per cent and there was no cure or effective treatment beyond fluid replacement and supportive care, intensive work began then to produce a vaccine against Ebola in the shortest possible time.

The first reportedly successful experimental Ebola vaccine was described in the medical journal The Lancet on December 22, 2016. The journal said the vaccine — a recombinant, replication-competent vesicular stomatitis virus-based candidate vaccine — was 100 per cent effective in preventing the disease after 10 days in the 5,837 people who had received it in Guinea and Sierra Leone. During the same time frame, 23 of the 4,507 people who did not receive the vaccine, contracted the virus.

EBOLA ON THE DECLINE

EBOLA ON THE DECLINE

The study was conducted by researchers from the World Health Organization (WHO), but as the Ebola epidemic was on the decline in the area, the researchers enrolled people who were close contacts, as well as contacts of contacts, of people who had contracted the disease. Only people aged 18 years and older, who were not ill or pregnant, were eligible for the study.

The research was done as a phase three trial in which all the sick people’s contacts were randomly assigned as a group to receive the experimental vaccine, either immediately or after a 21-day delay.

The immediate vaccination group had more high-risk contacts in their clusters. When the vaccine began to show effectiveness, an independent safety monitoring board recommended that the vaccine be offered immediately to all eligible contacts, including children aged six years and older.

ANOTHER VACCINE

ANOTHER VACCINE

In the same edition, The Lancet also described the successful results of another Ebola vaccine, a recombinant adenovirus type five-based vaccine; this one tested in a phase two trial, which is not yet as comprehensive as a phase three trial.

Research on experimental treatments are customarily first done in animals to ascertain good effects before being permitted in humans. When first tested in humans in so-called phase one trials, only a small number of healthy volunteers are involved. At this stage, the primary focus of the testing is safety and toxicity levels in humans. Once satisfactory, the drug or vaccine goes on to phase two trials involving larger numbers of research participants with great attention to both the safety and effectiveness of the product.

Phase three research trials customarily involve several hundreds and sometimes thousands of people who are randomly assigned to different groups — some to receive the treatment and some not — and the outcomes in the various groups are compared to ascertain if the treatment is successful.

The phase two research trial described in the journal involved healthy volunteers and was conducted by researchers from Nanjing, China, and the Ministry of Health in Sierra Leone. Those results indicated that this vaccine was both safe and highly immunogenic, as 94 per cent of the 500 individuals enrolled in the trial showed seroconversion after one month, thus indicating a positive protective result. The previous studies in animals had also shown a consistently high and rapid protection. However, the positive response in this vaccine had decreased by 85 per cent at six months after injection, suggesting that a booster may be needed.

CAUTION

CAUTION

Implementing a research trial during a devastating outbreak is far from an ideal situation, but the researchers from the phase three trial noted that their findings indicate that it is feasible to undertake efficacy trials in the most challenging epidemic circumstances.

Whilst the vaccine appears to be highly effective and safe when used in the context of disease outbreak, some questions remain. These include the long-term efficacy (effectiveness in protecting) of the vaccine and whether future formulations of the vaccine could reduce the number of adverse events without reducing its effectiveness.

In the phase one trial of this vaccine, that is when first tested in humans, 13 of the 51 research participants had reported experiencing oligo-arthritis, the most common type of arthritis affecting juveniles and young people, involving their knees. During the phase three trial, despite its demonstrable effectiveness, participants reported experiencing mild adverse events such as headache, fatigue, muscle pain, and pain at the injection site.

Despite the foregoing, however, when Ebola threatens our lives, I am certain we all would bear these side effects willingly if we feel a vaccine is likely to protect and save our lives.

Nevertheless, we’ll have to wait and see whether, upon production, the vaccine will be affordable for those who may need it the most.

Derrick Aarons MD, PhD is a consultant bioethicist/family physician, a specialist in ethical issues in medicine, the life sciences and research, and is the Ethicist at the Caribbean Public Health Agency – CARPHA. (The views expressed here are not written on behalf of CARPHA)

Derrick Aarons MD, PhD is a consultant bioethicist/family physician, a specialist in ethical issues in medicine, the life sciences and research, and is the Ethicist at the Caribbean Public Health Agency – CARPHA. (The views expressed here are not written on behalf of CARPHA)