THE DEATH OF a woman who worked at a Russian laboratory where plague is studied has led to rampant speculation and conspiracist claims online. 

One of the conspiracy theories attempts to link the development of a plague vaccine by scientists in Israel to the death of the woman in Russia, implying that the two events happened suspiciously close together. 

On 2 October, media reports first emerged that a woman who worked at the Irkutsk Antiplague Research Institute in Siberia had died. Russian authorities said there was no evidence that she was infected with lab material, but the World Health Organization (WHO) has requested further information. 

“They’re developing an mRNA vaccine for the plague. Coincidentally just when a plague lab leak has killed one person in Russia,” reads one post on X seen hundreds of thousands of times and shared by an account with one million followers. 

It has not been confirmed that the woman died from pneumonic plague infection.

The WHO’s director said on 7 October that the lab worker in Siberia “died after being hospitalised with severe pneumonia”.

“No microorganisms linked to the woman’s work had been found in her biological samples,” Irkutsk’s governor said.

Coincidence? 

Numerous posts online have claimed or implied that the death of the Russian lab worker and the development of an mRNA vaccine for pneumonic plague are linked because they occurred close together. 

“Israel preemptively produced a pneumonic plague vaccine just before a Russian lab technician broke a vial, released the pathogen, and died,” reads one post on X that has been viewed more than 65 thousand times.

“Israel has created a 100% effective vaccine to save us, just in the nick of time. How perfect!!” reads another. 

The problem with this theory is that the development of the mRNA vaccine did not coincide with the death of the lab worker in Siberia. 

The woman’s death was first reported on 2 October 2026. The Israeli vaccine has been in the works for years. 

The experimental vaccine was developed by researchers at Tel Aviv University, who worked alongside the Israel Institute for Biological Research.

Their findings after successful trials in mice were published in the journal Advanced Science in April 2025, but the university was promoting the research as early as March 2023. 

The researchers said the vaccine was 100% successful when tested on mice, but that more testing would need to be done on non-human primates before it could be tried on humans. 

Not the first vaccine

The vaccine being developed in Israel is the first of its kind because it uses mRNA, much like the vaccine for Covid-19 does. But it is not the first vaccine for plague. 

There have been plague vaccines in existence since the late 19th century. The first was developed in India in 1897. 

According to Gavi, the Vaccine Alliance, a public-private organisation that funds vaccine immunisation programmes worldwide, these early vaccines are limited in their effectiveness. 

This is why new vaccines are being developed and in 2018 the WHO published a plan for the development of safer and more effective ones.

Additionally, pneumonic plague and other variants can be treated with antibiotics, although they must be administered within 24 hours.

Because the window for antibiotic intervention is so small, vaccines are seen as a way to preemptively tackle outbreaks of the disease, especially in poor countries where treatment may not be readily available. 

The misinformation about the Israeli-made plague vaccine aligns with similar theories that emerged around the time of the Covid-19 pandemic, which some people claimed was a hoax designed to boost the profits of pharmaceutical companies. 

The Journal’s FactCheck is a signatory to the International Fact-Checking Network’s Code of Principles. You can read it here. For information on how FactCheck works, what the verdicts mean, and how you can take part, check out our Reader’s Guide here. You can read about the team of editors and reporters who work on the factchecks here.