Ebola virus causes an untreatable haemorrhagic fever, which is fatal in 90% of cases. Now, the production of a vaccine that can confer protection against Ebola virus in macaque monkeys only 28 days after immunization could mean that a vaccine can be administered in outbreak situations.

The Ebola virus glycoprotein (GP) — an envelope protein — is the main pathogenic determinant during infection. Previously, immunization with a DNA vaccine containing genes encoding GP from several Ebola virus serotypes and nucleoprotein (NP), followed by a booster with a recombinant adenovirus vector containing GP from the Zaire Ebola virus subtype — a 'prime–boost' strategy — generated protective cellular and humoral immunity in macaques. But the prime–boost regime took six months to administer. Now, Sullivan et al. have developed a vaccine that contains an equal mixture of recombinant adenovirus vectors encoding Ebola virus (Zaire and Sudan serotypes) GP and NP. One shot of this vaccine protects against Ebola virus challenge in macaques 28 days after immunization. With the one-shot vaccine, protection was achieved against low and high challenge doses of Ebola virus — both of which were lethal for saline-injected control macaques. Protection correlated with the generation of Ebola-virus-specific CD8+ T-cell and antibody responses.

Intriguingly, Ebola-virus-specific immune responses did not increase markedly after a second round of vaccination, probably because of anti-vector immunity. Adenovirus is one cause of the common cold — and 45% of the United States population have adenovirus-specific antibodies. The authors speculate that using different adenovirus serotypes as vaccine vectors could help to overcome potential problems with resistance to these vaccines. Because Ebola virus typically causes outbreaks that are spread in healthcare settings, this new vaccine could help to control outbreaks if it proves to be similarly effective in humans.