It was only last year that Nobel laureate Drew Weissman spoke with complete confidence about the mRNA technology he helped create.

When asked whether the genetic material or lipid nanoparticles (LNPs) used in Covid-19 vaccines could persist in the body or spread far beyond the injection site, his answer was unequivocal.

“It is absolutely impossible….. The RNA is gone in days,” said Weissman, who shared the 2023 Nobel Prize in Medicine for co-inventing the technology

But four years earlier, behind closed doors, his message was very different.

Newly released documents made public by Senator Rand Paul reveal that Weissman privately alerted Anthony Fauci to some concerning findings from his own laboratory.

Those findings triggered discussions among some of the NIH’s most senior vaccine scientists before eventually finding their way into Fauci’s personal diary.

Still emerging technology

When the pandemic hit, mRNA vaccines were still an emerging technology. Just two years prior, Weissman and his colleagues published a review in Nature Reviews Drug Discovery.

While praising the technology’s potential, they highlighted unresolved hurdles—including RNA instability, unwanted immune reactions, and the challenge of getting genetic material into the right cells.

Though initial animal studies showed promise, early human trials yielded modest results, leading the authors to urge “cautious expectations.”

Significant questions also remained around safety of mRNA vaccines during pregnancy, as pregnant women were excluded from the pivotal Pfizer and Moderna trials.

Regulators had to rely on animal reproductive data while human data accumulated post-rollout.

It was against this backdrop that Weissman reached out directly to Fauci.

Fauci alerted to new data

On 8 February 2021, Weissman emailed Fauci.

“I wanted to alert you to some new data we generated.”

Weissman reported that when injected into pregnant mice, mRNA-LNPs crossed the placenta and entered the foetus, generating viral proteins and triggering an immune response in the amniotic fluid.

In non-pregnant mice, the LNPs accumulated in the uterus and ovaries.

While these initial experiments used intravenous (IV) delivery at doses roughly 100 times higher than a standard vaccine, they aligned with broader research.

As early as 2013, French scientists had shown that lipid nanoparticles could accumulate in organs such as the ovaries, highlighting the need to understand how different delivery methods behave inside the body.

This was also reflected in regulatory documents for Covid-19 vaccine pre-clinical studies, which showed that mRNA lipid nanoparticles accumulated in organs, including the ovaries.

Weissman wanted to test a more clinically relevant scenario, so he planned to repeat the study using intramuscular (IM) injections, matching standard vaccination practices.

“We are waiting to release the findings until these studies are completed,” Weissman told Fauci, noting he had already alerted the FDA, Moderna, BioNTech/Pfizer, and DARPA.

Fauci replied that evening.

“It would be interesting to see what human dose levels given IM do.”

Three weeks later, on 1 March 2021, Weissman emailed back with a confidential report attached.

“Here is the human dose IM studies in pregnant mice. We still have some concern over the data,” he wrote.

Within the hour, Fauci forwarded the report to Dr John Mascola, director of the NIH Vaccine Research Centre, writing, “Let us discuss.”

Mascola quickly circulated the report to his senior leadership team for review.

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IPAK-EDU is grateful to MD REPORTS as this piece was originally published there and is included in this news feed with mutual agreement. Read More