A news story headline(1) is making the rounds that's really confusing and scaring people that don't understand how viral infections or how vaccines work. Even though the article itself is reasonable only the headline is being promoted rapidly via social media and in a very negative light.
So, what happened?
Well, the story is true. A nurse was administered one of the new COVID-19 mRNA vaccines; and yet, six days later, she tested positive for COVID-19. Isn't this disastrous?! Well, no. Not even close. Here are a few points to help put your mind at ease.
1.) Did the vaccine give her COVID? No, the vaccine didn't give her Covid-19. It causes some of your cells to present the same spike proteins that viruses have on their surfaces to trigger an immune response but without the infectious agent(1). This is similar to how an inactivated viral vaccine may have the proteins present but it is not infectious.
2.) But she had the vaccine?! Yes, but for now, two vaccinations are required(2). The immune response may be partial, depending on the vaccine, yet still effective after the first injection, with eventually achieving a 90-95% immunity within 10 to 14 days after the second dose. It is certain she was already infected at least within 10 days before getting the vaccine.
3.) But vaccines give you the virus and can make you sick. Not quite. Yes, you may feel mildly ill after a vaccine, this doesn't mean you have COVID-19. This is your body reacting naturally to a foreign agent. It is doing its job. Prepping your immune system to kick viral butt the next time it sees COVID in its house.
4.) But I tested positive for COVID after the vaccine. Yes, you could have been infected prior. Also, if an antibody test is given, you may still test positive for COVID-19, as you now have antibodies to the viral proteins. This doesn't mean you have an active infection.
5.) I am now immune no matter what now, right? You can still catch a viral infection even after getting a vaccine against a particular viral pathogen. It is not guaranteed. This is why you get booster shots to recharge your immune system against disease variants. Research is currently being done on the effectiveness of current vaccines on COVID variants.
(1) News story: https://abcnews.go.com/Health/nurse-tests-positive-covid-19-shortly-vaccinated/story?id=74947995
(2) Good explanation of how the vaccine works here: https://www.wistv.com/2020/12/14/explainer-how-does-covid-vaccine-work
(3) Only two vaccines have been approved in America and they both require two doses. Future vaccines may not. More information about the recently approved vaccines from Pfizer and Moderna: https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-vaccine/art-20484859