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Our factcheck looks at a claim about a Cuban cancer vaccine. (Shutterstock) Our factcheck looks at a claim about a Cuban cancer vaccine. (Shutterstock)

Our factcheck looks at a claim about a Cuban cancer vaccine. (Shutterstock)

Jon Greenberg
By Jon Greenberg March 4, 2020

Pro-Sanders post said US sanctions blocked access to a Cuban lung cancer vaccine. Is that true?

If Your Time is short

  • Cancer vaccines don’t prevent disease; the focus is on slowing tumor growth.

  • The Cuban vaccine Cimavax was developed in the 1990s and extended life by about three months in trials there.

  • After the United States normalized relations with Cuba, the drug became available for a small clinical trial in the United States in 2016. American access to the drug remains limited.

Online supporters of Bernie Sanders came to his defense on the issue of Cuba, touting the communist island nation’s accomplishments beyond improving literacy rates.

"Cuba has a lung cancer vaccine we in the US had no access to because we sanctioned Cuba," the Feb. 24 post said. "Cuba eliminated HIV transmission from mother to child. Cuba has a literacy rate of nearly 98% now."

The post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.)

We’ll focus on the claim about the lung cancer vaccine because the facts behind the statement lead to a less certain conclusion than the Facebook post suggests. (The other elements in the post are accurate.)

What is a cancer vaccine?

Though we tend to think of vaccines as protecting you from getting sick, cancer vaccines work differently.

In 2016, nearly 150,000 people died from lung cancer in the United States. Neither the United States nor Cuba nor anyone else has developed a vaccine that would stop those deaths.

That’s because cancer vaccines don’t block disease; their purpose is to shrink existing tumors, and failing that, slow them down.

There are 91 lung cancer vaccines under study today in the United States, according to the National Institutes of Health.

Cuba’s cancer vaccine

During the 1990s, Cuba began testing a drug called Cimavax and found that it extended lung cancer patients’ lives by about three months

In 2011, Cuba began offering the drug to Cubans for free. That same year, Cuban researchers discussed the results with the Roswell Park Cancer Institute in Buffalo, N.Y.

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Four years later — the same year that the United States and Cuba re-opened embassies in each other’s capitals — scientists from both countries agreed on a collaborative research project. It was the first time since the Cuban revolution that Cuban and American institutions had been permitted to engage in such a joint venture, Roswell Park’s chief executive, Candace S. Johnson told the New York Times.

Did lifting the embargo give U.S. patients access to Cimavax?

The initial results in Cuba were ambiguous, and they needed to be replicated in the United States to meet Food and Drug Administration rules.

Ultimately, the Roswell Park study hopes to have 180 patients. These are people with advanced cancer who have exhausted other treatments. So far, the study has not met its goal.

Approximately 100 people have gone to Cuba on their own for treatment.

With about 200,000 new cases of lung cancer each year, the fraction of patients accessing Cimavax is about one tenth of one percent.

When the Trump administration re-imposed restrictions on travel to Cuba, it created a legal bind for Americans — about 100 since 2016 — who have gone there for this treatment. According to the new rules, they were now breaking the law. 

But this highlights that opening the doors to Cuba also increased access to the drug, although access was limited to patients who could afford to make the trip.

Our ruling

A Facebook post said Cuba had a lung cancer vaccine that the United States had no access to due to the decades-long embargo. There is an element of accuracy here, but it lacks several important pieces of information. 

A lung cancer vaccine doesn’t prevent the disease; it is judged a success if it slows down or stops tumor growth. The drug in this case, Cimavax, extended life by about three months in the Cuban study. Access to Cimavax is limited to about 180 patients in one American study and those who go on their own to Cuba. The combined total represents a tiny fraction of people with lung cancer. 

There are about 90 cancer vaccines under study in America today. None of this would be apparent to people who read the Facebook post.

We rate this claim Half True.

Our Sources

Facebook, Post, Feb. 24, 2020

National Institutes of Health, Clinical trials, Dec. 12, 2019

National Institutes of Health, Lung cancer vaccine studies, accessed Feb. 28, 2020

Roswell Park Comprehensive Cancer Center, About Roswell Park’s Cuban Collaboration, September 2018

Methods in Molecular Biology, Cancer Vaccines: A Brief Overview, 2016

US News and World Report, What to Know About the CIMAvax Lung Cancer Vaccine, Nov. 9, 2017

ABC News, 3 of Cuba's Major Medical Achievements, Nov. 29, 2016

Medium, Cuba has a lung cancer vaccine. Many US patients can’t get it without breaking the law., Jan. 9, 2018

Public Radio International, Cuba has had a lung cancer vaccine for years, accessed March 3, 2020

New York Times, A Souvenir Smuggled Home From Cuba: A Cancer Vaccine, Nov. 14, 2016

PolitiFact, Fact-checking Bernie Sanders' claim on Cuba literacy under Castro, Feb. 24, 2020


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Pro-Sanders post said US sanctions blocked access to a Cuban lung cancer vaccine. Is that true?

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