Thread by @jeffgilchrist

COVID-19: No, vaccinated people are not as likely to spread COVID

In Ontario rates at which people are becoming infected, hospitalized, and admitted to the ICU are much higher for people who have not been COVID-19 vaccinated ( gilchrist.ca/jeff/COVID-19/… ). 🧵1/

This article does a good job at explaining why vaccinated people are not as likely to spread COVID-19 ( theatlantic.com/ideas/archive/… ). 2/

There has unfortunately been a lot of misinformation given, and confusing messaging from public-health agencies. The reality is that in order to spread COVID-19 and infect someone else you need to actually be infected yourself. 3/

People who are fully vaccinated are far less likely to become infected, period. If someone isn't infected, they can't spread the virus to others. 4/

While breakthrough cases can happen in someone who is fully vaccinated and the viral load can become as high as an unvaccinated person, studies have shown they are likely contagious for a shorter period of time ( medrxiv.org/content/10.110… ). 5/

Studies have also shown the fully vaccinated harbour less infectious virus overall ( medrxiv.org/content/10.110… ). 6/

Even the few vaccinated people who can spread the virus are doing so at a much lower rate than someone who is unvaccinated. That is why getting more people vaccinated is crucial for controlling the spread of COVID-19. 7/

Every vaccinated person helps limit the virus' ability to hide, replicate, and propagate. The author of the article uses an analogy that among the unvaccinated, the virus travels unhindered on a highway with multiple off-ramps and refueling stations. 8/

In those people who are vaccinated, the virus gets lost in a maze of dead-end streets and cul-de-sacs. Every once in a while it pieces together an escape route but in most scenarios it finds itself cut off and its journey ends. 9/

How common are breakthrough infections? NYC has released its post-vaccination outcomes report with data from Jan. 17, 2021 to Aug. 7, 2021 ( www1.nyc.gov/assets/doh/dow… ). 10/

They found that the fully vaccinated accounted for:
0.33% = COVID-19 cases
0.02% = COVID-19 hospitalizations
0.003% = COVID-19 deaths

11/

In NYC at the beginning of August, an unvaccinated person was 3.1 times more likely to become infected than a fully vaccinated person. 12/

In Ontario right now, an unvaccinated person 18-59 is 7 times more likely to become infected, 15.4 times more likely for children 12-17, 13.4 times more likely for adults 60-79, and 22.9 times more likely for adults 80+ ( gilchrist.ca/jeff/COVID-19/… ). 13/

An example is provided of 2 weddings with 100 guests, one where everyone is COVID-19 unvaccinated and the other where all the guests are fully vaccinated. In the unvaccinated wedding group, the likelihood that at least 1 guest has COVID-19 is much higher. 14/

Everyone who is present is more susceptible and the Delta variant will likely infect many others. 15/

At the wedding with exclusively vaccinated attendees, the likelihood that anyone present has COVID-19 is much smaller (each person is 85% less likely to be infected than an unvaccinated person in Ontario). 16/

Even if someone present is infected, the likelihood that other guests will become infected is similarly low given the additional protection afforded by the vaccine. 17/

This is why vaccine mandates are so important and events that exclude unvaccinated people are considerably safer than those that are open to all. 18/

On top of the vaccine protecting the individual who gets it, the more people that become vaccinated, the more it helps keep everyone else protected as well, including children and others ineligible for vaccination. 19/

Since fully vaccinated people can become infected and spread the virus to others, it is still important they do their part and follow all public health guidelines including wearing masks and physical distancing where required. 20/