No, vaccines do not increase the risk of spreading serious illness or death to the unvaccinated

Of all the distressing information circulating online about COVID and vaccines, this claim can have significant impact on what may be the most crucial health decision one can make: whether or not to get vaccinated.


Spread globally in English and appearing in Bulgarian and other languages the claim contains two components:

1) The vaccine alone is enough to make the vaccinated infectious to others

2) The vaccinated present a greater risk to others by contracting the virus elsewhere and retransmitting it

Both are false.

1) FALSE: The vaccines cause the vaccinated to be infectious to others.

There are two types of vaccines against COVID-19 authorized in the European Union: mRNA (Moderna and Pfizer-BioNTech) and Viral Vector (Johnson and Johnson and AstraZeneca).

mRNA vaccines contain laboratory-produced mRNA.  After being injected into muscle tissue, the messenger molecules teach the body’s cells how to make a protein which enhances the body’s ability to recognize COVID-19 and fight off future infection. As it spreads through the body, the mRNA triggers the immune system and creates antibodies so the body is already prepared to fight off a future COVID infection if and when it occurs.

For more on how mRNA vaccines work see this explanation by the CDC.

Or this by the European Vaccination Information Portal in Bulgarian.

For visualization of how mRNA vaccines work, watch this video by the PBS NewsHour.

Viral Vector vaccines use harmless versions of a different virus. Similar to mRNA vaccines, they also teach the body’s immune system to create the spike proteins needed to recognize and fight off an infection by COVID-19. The viruses are harmless and can not make you sick.

For more about how viral vector vaccines work see here:  https://myhealth.ucsd.edu/Coronavirus/134,264

Or in Bulgarian here at the European Vaccination Information Portal:

“An infection is an event when you exhale something which is a living biological agent capable of setting foot in another host in order to replicate or multiply,” says Dr. Petar Markov, an epidemiologist and lecturer at the London School of Hygiene and Tropical Medicine.

“You can only be infectious if you have a living virus,” says Dr. Markov. Such infections are caused by vaccine “shedding” and are only possible when vaccines contain live viruses.

Can any of the currently approved COVID vaccines turn the vaccinated into a vector for further spreading the virus?

According to the Centers for Disease Control and Prevention in the U.S. in this fact sheet:

“No. Vaccine shedding is the term used to describe the release or discharge of any of the vaccine components in or outside of the body. Vaccine shedding can only occur when a vaccine contains a weakened version of the virus. None of the vaccines authorized for use in the U.S. contains a live virus. mRNA and viral vector vaccines are the two types of currently authorized COVID-19 vaccines available.”

2) FALSE: The vaccinated present a greater risk of contracting the virus and transmitting it to others

Yes, the vaccinated ARE able to infect the unvaccinated by retransmitting the virus. But they present a much LOWER risk than the risk of the unvaccinated infecting the unvaccinated.

According to Dr. Markov, there are two factors which determine the risk of infection by those who carry the virus which causes COVID-19: viral load and opportunity for transmission.

The viral load is the quantity or concentration of the virus, generally in your lungs, mouth or nose. The load can vary from very little – small enough to present no risk to others – to a large load which creates a serious risk of infecting others.

The opportunity for transmission is the ability to expel the virus in a way that infects others: generally by exhaling aerosol or by expelling liquid droplets. These opportunities greatly increase when people are sick or show symptoms such as coughing, sneezing, having a runny nose or a swollen throat or bronchial or nasal mucus membrane.

“With an equal viral load, you are more contagious if you are more symptomatic,” says Dr. Markov. “You can’t be a transmitter unless both of these things are happening.”

All COVID-19 vaccines greatly reduce both viral loads and symptoms, in addition to the risk of serious illness or death, according to Professor Hristo Taskov, an immunologist and Professor at the Medical University Plovdiv and former director of the National Center of Infectious and Parasitic Diseases.

No vaccines are 100% effective and he estimates that approximately 5% of people who are vaccinated will not form an immune response. But he says that overall, the unvaccinated are some 5-10 times more likely to infect the unvaccinated than the vaccinated.

“Their viral load is higher and they shed more viruses, and the period during which they are infectious to others is longer — 10-14 days — while the period for the vaccinated is generally only a few days,” says Professor Taskov.

There is widespread public confusion about the benefit of vaccines for many reasons: mixed messages from public health officials and political leaders, new unpredictable risks created by the highly contagious delta variant, and rising numbers of breakthrough infections despite earlier predictions that infections would decrease.

As the share of the population that is vaccinated grows, so will the number of breakthrough infections, and increasingly as a result, infections spread by those with breakthrough infections. While there is a correlation between the events — more vaccinations, more breakthrough infections and the resulting increase spread by the vaccinated — vaccinations are not the cause of the increase. To the contrary, vaccinations are significantly reducing the numbers of those who would otherwise be infected, sick and dying from COVID-19.

As an illustration: 96% of traffic accidents in Bulgaria in the first nine months of 2021 involved drivers who were properly licenced, according to information provided for Factcheck.bg  by the Ministry of Internal Affairs (MVR). And as more people get licenses, the number of traffic accidents will likely grow as well. But that doesn’t mean that the increasing number of licenses is the cause of the increasing number of accidents. Or that drivers’ licenses should be eliminated. To the contrary: despite limiting personal freedoms, drivers’ licenses help keep a worsening problem from getting even worse.

The Appearance of Credibility and Red Flags

On the surface, the claim in the online post has the appearance of credibility. The site is produced by Greg Hunter, a former investigative journalist at CNN — a media organization with name recognition and credibility. Karen Kingston, the source he interviews, has years of experience working for leading reputable global pharmaceutical companies including Pfizer which produces COVID vaccines. She uses complicated scientific terminology and sounds well informed to readers with no scientific background. She presents the serious risks – death, serious illness –  in clear, immediate language.

But by scratching the surface, the veneer of credibility easily comes off. The article is based on only one source – a sign of a weakly supported claim at best and one which is completely false at worst. The second red flag: while Karen Kingston’s CV sounds impressive, she has no medical training. Yet this does not stop her from making a strong, unambiguous case about a crucial health decision with potentially fatal consequences.

By taking the next step and googling her name, Karen Kingston appears as the source for other dubious claims about vaccines. Factcheck.bg has already debunked another claim made by her — that vaccines contain nano particles of toxins including graphene oxide.

 A visit to the site where it was published shows other falsehoods about vaccines appearing alongside dubious claims about other topics: the War on God, the Deep State, the Communist takeover of the United States and other conspiracy theories.

Over the next month, Factcheck.bg will be reporting more on the background and motivations of disinformation purveyors who spread falsehoods online.

The publication has been produced with the support of NATO's Public Diplomacy Division. The responsibility for the content lies entirely with the editorial team of Factcheck.bg.

The publication has been produced with the support of NATO's Public Diplomacy Division. The responsibility for the content lies entirely with the editorial team of Factcheck.bg.

Matthew Brunwasser
Matthew Brunwasser
Journalist Matthew Brunwasser is a U.S. Fulbright Scholar (2020-21) researching disinformation in Bulgaria and working with the team of Factcheck.bg. He has been living and working in the Balkans for 20 years. Specializing in investigative journalism, human rights and international affairs, he has reported and produced stories from 30 countries in Europe, the ex-USSR, Africa and the Middle East for more than 40 international print, radio, online and television media including regular reports for The New York Times and The World broadcast nationally on U.S. public radio. He was an Investigative Reporting Fellow at the University of California Berkeley Graduate School of Journalism. He has also taught university-level investigative journalism courses in Bulgaria and Kosovo and advised international donors on media development projects in Eastern Europe. http://matthewbrunwasser.com/

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