Fact Check: Can Deadly Viruses Survive Vaccines?

A man in Africa developed Ebola for the second time after receiving a vaccine and fully recovering, but then had a relapse infection nearly six months later that was linked to 91 new cases before he tragically died, according to a recent report published in The New England Journal of Medicine.

Amid recent doubts about the longevity of COVID-19 vaccines' effectiveness, this raises the question: can deadly viruses survive vaccines?

More Ebola outbreaks create more survivors, raising the chances for relapse

The report of the Ebola relapse adds evidence to the idea that deadly viruses may lurk inside a human body long after symptoms subside, and suggests a need for survivors to continue monitoring their own well-being, and to work to prevent further transmission. But relapses like the one from the Democratic Republic of Congo's 2018 to 2020 outbreak are considered rare.

Indeed, this is the first such case that clearly spawned a major cluster of new cases. Early in March, scientists announced a separate outbreak in Guinea that appears to be linked to another one in West Africa — which ended five years ago. This means a survivor could have silently carried the virus for years before they spread it to Guinea.

"The most important message is, someone can get the disease, Ebola, twice and the second illness can sometimes be worse than the first one," explained Placide Mbala-Kingebeni of the University of Kinshasha — who assisted with research in the Congo cases — in an AP News report. The more Ebola outbreaks happen, the more survivors, and the more risk is posed to others via relapse, he added.

Typically, Ebola outbreaks start when someone contracts the virus from local wildlife. But then it spreads between people via bodily fluids and contaminated materials — with symptoms including sudden fever, muscle pain, sore throat, rashes, headaches, vomiting, bleeding, and diarrhea. A quarter to 90% of people die from infection.

Gene testing in relapsed patient showed identical Ebola virus, not reinfection

The recent report involved a 25-year-old motorcycle taxi driver who was vaccinated in December 2018 after coming into contact with a person who'd contracted Ebola. Later, in 2019, the taxi driver developed symptoms and was diagnosed with the deadly illness. This means he either didn't develop or simply lost his immunity in the next six months, said Michael Wiley, a virus expert at Nebraska Medical Center, to AP News.

The taxi man's blood tested negative for Ebola, twice, before he was discharged. But semen can carry the virus for more than a year — and, while the man's semen tested negative for Ebola in August of that year, he never returned for a repeat. This means men are strongly advised to continue periodic tests post-recovery.

Later, in November, the man again developed symptoms and sought care at a health facility from a "traditional" healer. Since his condition worsened, he was moved to an Ebola treatment unit. But the next day, sadly, he expired. Subsequent gene testing revealed the virus from his new illness showed nearly identical features to his initial one, which implies a relapse instead of a subsequent and distinct infection, said Wiley. Further testing revealed that the man had also spread the virus to 29 others, who in turn spread it to 62 more.

Too soon to say whether coronavirus latency poses a threat

Understandably, there exist suspicions in the public that a similar relapse could happen in a patient pre-diagnosed with COVID-19 who received a vaccine and recovered. If such vaccine recipients developed the same disease, the worry is that they may spread it to others via close contact, rendering vaccines a less viable solution to the coronavirus crisis. Admittedly, these concerns are not entirely without merit, since a recent poll found that a large scientific consensus believes the majority of first-gen vaccines will become ineffective within one year.

However, this relatively short timeframe stems from the coronavirus' impressive capacity to adapt and mutate — for example, as it has in the case of the South African, U.K., Brazil, or California variants of the COVID-19 illness — and not a relapse of an identical virus, like in the Ebola case above. While other viruses like the one linked to chickenpox can reactivate and cause shingles decades after the first infection, this has no material bearing on whether a coronavirus can also reactivate.

"We haven't seen yet this kind of latency from people who survived coronavirus," said World Health Organization Scientist Ibrahima Soce Fall, to AP News. Even in Ebola's case, "after six months, most of the patients completely clear the virus." In other words, it's too soon to say for certain whether specific COVID-19 coronavirus strains can survive and re-emerge after a latency period. But whether they can or can't, "[w]e need to make sure that survivors are not stigmatized," said Fall.