By Eric Levenson | CNN
On December 18, a nurse in the San Diego emergency room received an injection of the Covid-19 vaccine. A week later, he tested positive for the virus, CNN KGTV affiliate said.
Stories like this will become more common as millions of Americans receive the Pfizer-BioNTech and Moderna vaccines in the coming months. Over time, many of those vaccinated will still be infected with the new coronavirus.
But vaccines have proven to be 95% effective, so how can this happen?
See how:
Immunity does not take effect immediately
It takes time for vaccines to develop immunity, and the two vaccines authorized against the coronavirus require two doses, administered several weeks apart, to train the body’s immune system. People can be exposed to the coronavirus just before they are vaccinated, or shortly thereafter, and there will be no time for the body to develop its defenses.
The Centers for Disease Control and Prevention say that building immunity “usually takes a few weeks”.
“This means that it is possible that a person is infected with the virus that causes Covid-19 before or shortly after vaccination and is still sick,” says the CDC.
The 95% efficacy number for Covid-19 vaccines also assumes some built-in waiting time. Moderna measured the effectiveness of its vaccine from 14 days after the second dose, while Pfizer measured from seven days after the second dose.
Vaccines may not provide perfect protection
No vaccine is 100% effective, and coronavirus vaccine manufacturers are still evaluating whether vaccines protect against all infections or just those that cause symptoms.
The CDC estimates that 40% of coronavirus infections do not cause symptoms, and testing of the Moderna and Pfizer / BioNTech vaccines only looked at whether the vaccines prevented symptomatic infections.
Moderna said in December that it submitted data to the U.S. Food and Drug Administration showing that its vaccine prevented 2/3 of all infections, including asymptomatic infections. For now, the CDC recommends that people do not assume that they are completely immune to infection after being vaccinated.
Overall, both vaccines provided about 95% protection in clinical trials – meaning that 5% of people can still catch the virus even after two vaccines. In broader use, this rate of effectiveness may decrease as people with varying levels of immune response are vaccinated and then go out into the world.
It’s not because the vaccine gave you the virus
Current coronavirus vaccines cannot infect anyone with the virus. They do not contain the virus.
Instead, they carry a small piece of genetic material known as messenger RNA or mRNA. It instructs the body’s cells to make a small piece of material that looks like a part of the virus. These bits, in turn, are recognized by the immune system as a foreign invader, which starts to produce antibodies and immune cells that can recognize and neutralize the virus if the vaccinated person is exposed.
“None of the authorized and recommended COVID-19 vaccines or COVID-19 vaccines currently in development in the United States contain the live virus that causes COVID-19. This means that a COVID-19 vaccine cannot make you sick with COVID-19, ”says the CDC.
Immunity may decline over time
No one knows how long vaccines will protect people from infection.
Coronavirus has only been around for a year, and the final stages of testing vaccines ended just a few weeks ago. Pfizer and Moderna followed the volunteers for at least two months after the second dose.
The protection provided by vaccines may weaken over time and some vaccines require a booster injection years later. For example, the CDC recommends that adults have an injection of tetanus reinforcement every 10 years. During outbreaks of measles or mumps, the CDC says that some people “may be recommended” to receive an additional dose of MMR vaccine for additional protection.
There is also the possibility that the new coronavirus may mutate in a way that makes vaccines less effective. Strains of the flu virus are constantly mutating, which is one of the reasons why people need new flu shots every year.
Doctors hope that the coronavirus will not mutate as it does with the flu. If that happens, however, the technology used to make the new coronavirus vaccines is designed to be easily adapted. It should take much less time to update the Moderna and Pfizer vaccines than it is to make new flu vaccines.
Others may not be protected from you
Health officials at Dr. Anthony Fauci onwards are warning people that no one can discard facial masks and social detachment behavior just because they have been vaccinated.
That’s because even people who are immune to the virus can be exposed to it and pass it on to others. It can grow on the nose, says Fauci, director of the National Institute of Allergy and Infectious Diseases.
“It is possible for someone to receive the vaccine, but still be an asymptomatic carrier,” said CNN medical analyst Dr. Leana Wen, an emergency physician. “They may not have symptoms, but they have the virus in their nasal passage so that if they are talking, breathing, sneezing and so on, they can still pass it on to others.”
Given these unanswered questions, the CDC says that vaccinated people should still use “all the tools available to us” to stop the pandemic, including wearing a mask and staying at least 2 meters away from other people.
The-CNN-Wire
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