Fact Check-COVID-19 vaccines are not infectious; you can’t transmit the vaccine to an unvaccinated individual

Claims that COVID-19 vaccines have been designed so that recipients can transmit their inoculations have revealed misunderstandings of how these vaccines work. Vaccines against the novel coronavirus are not infectious and cannot be passed from person to person.

The claim was initially made in a Facebook post comprising several screenshots from webpages that discuss the potential of future “self-spreading vaccines”. In the post’s caption, the user writes: “It’s not shedding, it’s intentional transmission.” (here)

Comments left underneath the post reveal a further misconception: “Help me understand does it mean donated blood from vaxxed/jabbed people will transmit the spike protein and consequently the patient gets to exhibit all the auto response immune system symptoms?” one user asks.

“Yep. They transmit it through their pores, saliva, faeces, blood etc. They are time bombs,” another replies.

“Shedding” is a term that was frequently used in the early days of the pandemic to describe people transmitting or emitting coronavirus particles. However, experts have told Reuters that people cannot “shed” COVID-19 vaccines. This topic has been addressed (here) and (here).

Meanwhile, the suggestion that COVID-19 vaccines have been designed for “intentional transmission” is also false.

While the possibility of researchers creating self-disseminating vaccines has been discussed in scientific literature (here , here , here) , this is not something that has been rolled out in humans. It would involve genetically engineering a vaccine so immunity spreads through an animal population like a disease, rather than the disease itself spreading. Scientists note the potential risks associated with this (here).

Transmission would also require the vaccine to be live – and to be able to replicate and infect its host. This is not possible. None of the COVID-19 vaccines have this capability.

The mRNA shots developed by Pfizer/BioNTech and Moderna “contain only instructions for making spike protein and are incapable of generating virus particles, so nothing can be shed”, said Dr Daniel Kuritzkes, chief of the infectious diseases division at Brigham and Women’s Hospital, one of the world’s top teaching hospitals and part of Harvard Medical School, in a statement emailed to Reuters.

Likewise, the Johnson & Johnson (also referred to as Janssen) vaccine “is based on a replication-defective adenovirus, which means the adenovirus is incapable of reproducing”, he added. The Oxford/AstraZeneca jab uses the same mechanism (here).

Kuritzkes also pointed out that the mRNA vaccines are degraded within 24 to 48 hours. As explained (here), that means they disappear from recipients’ bodies within a day or two. Similarly, the J&J vaccine “gets taken up into cells where it is injected, makes spike protein, and is degraded. It cannot disseminate to other tissues or be shed”, Kuritzkes said.


False. COVID-19 vaccines are not infectious, and they cannot spread between people. The mRNA vaccines authorised for emergency use do not use a live virus, while the Johnson & Johnson and Oxford/AstraZeneca jabs use a harmless adenovirus that has been modified to prevent replication.

This article was produced by the Reuters Fact Check team. Read more about our fact-checking work  here .