100% Effective Vaccine

A few days ago I was reading random stuff on the internet, as is one’s procrastination proclivity, catching up after the holiday, and I exclaimed out loud: “They discovered an 100% effective Ebola Vaccine!”. I expected some ‘yeay’-s or at least some grunts along the lines of ‘that’s nice’ or ‘cool’. Naturally, I turned around from my computer to check the source of unaccustomed silence to the announcement of such good news or, at least, to make sure that everybody is still breathing and present in the room. What met my worried glare was a gloom face and a shaking head. That’s because news like that are misleading, because, duh, it finally dawned on me, there is no such thing as ‘100% effective vaccine’.

And yet…, and yet this is exactly what Henao-Restrepo et al. (2016) say they found! The study is huge, employing more that 10 000 people. Such a tremendous endeavor has been financed by WHO (World Health Organization) and various departments from several countries (UK, USA, Switzerland, South Africa, Belgium, Germany, France, Guinea, and Norway) and, I’m assuming, a lot of paid and unpaid volunteers. I cannot even imagine the amount of work and the number of people that made this happen. And the coordination required for such speedy results!

The successful vaccine in rodents and non-human primates, called the recombinant, replication-competent, vesicular stomatitis virus-based vaccine expressing the glycoprotein of a Zaire Ebolavirus (rVSV-ZEBOV) has been taken to the Republic of Guinea and rapidly administered to volunteers who were in contact with somebody that had Ebola symptoms. And their contacts. I mean the contacts and the contacts of contacts of the Ebola patient. Who were contacted by the researchers within 2 days of a new Ebola case based on the patient’s list of contacts. And of contacts of contacts. Is not that complicated, honest.

After vaccinations, the “vaccinees were observed for 30 min post-vaccination and at home visits on days 3, 14, 21, 42, 63, and 84” (p.4). Some volunteers received the vaccine immediately, others after 3 weeks. No one who received the vaccine immediately developed Ebola, which lead the researchers to claim that the vaccine is 100% effective. Only 9 from the delayed vaccination group developed Ebola within 10 days of vaccination, but the researchers figured that these people probably contacted Ebola prior to the vaccination, since the disease requires typically about 10 days to show its ugly  horns.

So this is great news. Absolutely great. Even if, as always, I could nitpick thorough the paper, squabble over the “typically” 10-day incubation period, and cock an eyebrow at the new-fangled ring vaccination design as opposed to the old-fashioned placebo approach. Even after these minor criticisms this is – I repeat – GREAT NEWS!

P.S. Don’t ever say that the UN didn’t do anything for you.


Reference: Henao-Restrepo AM, Camacho A, Longini IM, Watson CH, Edmunds WJ, Egger M, Carroll MW, Dean NE, Diatta I, Doumbia M, Draguez B, Duraffour S, Enwere G, Grais R, Gunther S, Gsell PS, Hossmann S, Watle SV, Kondé MK, Kéïta S, Kone S, Kuisma E, Levine MM, Mandal S, Mauget T, Norheim G, Riveros X, Soumah A, Trelle S, Vicari AS, Røttingen JA, Kieny MP. (22 Dec 2016). Efficacy and effectiveness of an rVSV-vectored vaccine in preventing Ebola virus disease: final results from the Guinea ring vaccination, open-label, cluster-randomised trial (Ebola Ça Suffit!). Lancet. pii: S0140-6736(16)32621-6. doi: 10.1016/S0140-6736(16)32621-6. PMID: 28017403 [Epub ahead of print] ARTICLE | FREE FULLTEXT PDF | Good Nitpicking in The Conversation

By Neuronicus, 18 January 2017



Ebola survivors can still transmit the disease

Ebola patient treated in isolation. License: PD

Ebola is a nasty, nasty disease, incurable, extremely virulent, and with a high mortality rate. Its last devastating outbreak in West Africa in the past couple of years compelled the governments and pharmaceutical agencies to invest heavily in the search of a cure or a vaccine. As a result, there are already a dozen or so of possible vaccines being tested in various phases of drug development. Some hold real promise and, hopefully, one would breed true very soon.

But that’s not what today article is about. It is about the Ebola survivors. If the patient is still alive after two weeks from symptoms onset, there are very good chances s/he will survive it. Depending on the country, the survival rates vary between 10% up to 75%, with the average being about 50% (that is, you got one chance in two to survive Ebola).

It is very difficult to conduct thorough testing on Ebola survivors, mainly due to poor accessibility to them. However, Thorson et al. (2016) looked at all the available evidence, from published articles to non-peer-reviewed papers, from WHO data (World Health Organization) to personal communications and Internet feeds to see if Ebola survivors can still transmit the disease.

In short: yes, they can, unfortunately. Primarily through sexual transmission, as the authors found reports of Ebola being present in the sperm up to 284 days after symptom onset (and possibly even longer). Also, there are reports of sexual partners being infected by an Ebola survivor.

The authors (and the WHO) recommend that the survivors should be tested every 3 months and declared free of Ebola only when RT-PCR (reverse transcription polymerase chain reaction, a method that detects RNA expression) is negative twice. Meanwhile, Ebola survivors should practice abstinence. Or, use condoms, although the virus is really small (80 nm), therefore a condoms may not present an impenetrable barrier.

Reference: Thorson A, Formenty P, Lofthouse C, & Broutet N (Jan 2016). Systematic review of the literature on viral persistence and sexual transmission from recovered Ebola survivors: evidence and recommendations. BMJ Open, 6:e008859. doi:10.1136/bmjopen-2015-008859.  Article | FREE PDF

By Neuronicus, 10 January 2016