Covid-19 Vaccines and Transmission

Covid-19 Vaccines and Transmission

At the close of a tumultuous and challenging year, people celebrated the announcement that the FDA authorized use of two fast-tracked vaccines in the fight against Covid-19. The Pfizer-BioNTech vaccine received emergency use authorization on December 11th and the Moderna vaccine soon after, on December 18th. Globally, other vaccines have been approved and are being rolled out in other countries.

Now, about a month later, states have already begun administering the vaccines to hospital workers, residents of long-term care facilities, the elderly, and more. All of this is extremely exciting. It’s a crucial step in controlling Covid-19. But it is important to understand how the vaccines work (i.e. – what we know vs. what we don’t know—so far).

What We Know: Preventing Disease

Clinical trials have shown an astounding 90-95% efficacy rate in preventing disease. This means the vaccines are highly effective at preventing you, the vaccinated person, from getting sick from the disease. In other words, the vaccines prevent or greatly reduce symptoms associated with Covid-19.

In layman’s terms, vaccines work by tricking the body into producing antibodies before any actual infection. That way, if the vaccinated person ultimately becomes infected, the body already has antibodies ready to fight the virus. The Pfizer-BioNTech and Moderna vaccines are approximately 95% effective in preventing disease, even if the coronavirus is later introduced into your system. However, as discussed below, we don’t know if the vaccines affect transmission of the disease to others. In other words, we know the vaccines help prevent/reduce symptoms, but if you do get the virus (e.g. – an asymptomatic infection), do they help in stopping you from spreading it?

What We Don’t Know: Preventing Infection/Transmission?

The 2020 clinical trials for these vaccines were focused on determining if they can curb disease and symptomatology. Understandably, with limited data and time, these fast-tracked clinical trials did not examine whether the vaccines affect transmission. They prevent disease, but do they prevent infection? Simply put, we don’t know if the vaccines stop you from infecting others. There is not yet enough public health data to answer this question. However, as the vaccines are rolled out throughout the country, that data will become available. Researchers—including those involved in last year’s clinical trials—are already hard at work in implementing studies to examine this very issue. As such, it is simply a matter of time until we know the answer to the question of infection.


The Pfizer-BioNTech and Moderna vaccines are crucial in controlling Covid-19. Clinical trials have shown the yare approximately 95% effective in preventing disease/preventing you from getting sick (i.e. – reducing symptoms). However, we do not yet have data on if the vaccines actually reduce your risk of transmitting Covid-19 to other people. Even if you get the vaccine, you still run the risk of asymptomatically spreading the disease to others. As such, everyone—even those who have received a vaccine—should continue maintaining social distancing, wearing masks, hand washing/sterilizing and taking whatever other precautions necessary in this ongoing fight.



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Covid-19 Vaccines and Transmission

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