Imagine that you developed a runny nose and a sore throat last night. When you woke up this morning you started coughing and had a fever. During this past year, your mind would have immediately deduced covid-19. But if you’ve already received full vaccinations, you might think: should I get tested for covid-19?
As an infectious disease physician, this is a question I am frequently asked. The answer is yes. If you have symptoms of covid-19, you should get tested even if you are fully vaccinated.
You will not be at high risk of hospitalization or severe illness, but if you are infected you could transmit the virus to a person who is not yet vaccinated , who could become very ill.
Vaccines work but they are not 100% effective
Researchers have developed some amazing covid-19 vaccines over the past year.
The high efficacy of these vaccines in tightly controlled clinical trial settings is similar to their effectiveness in real life. The mRNA vaccines made by Pfizer and Moderna continue to be more than 90% effective in preventing hospitalization or death.
However, that does not mean that you would have the same degree of protection against infection.
The most recent studies estimate that mRNA vaccines offer 70% to 85% protection against infection. It is impossible to know if a person is fully protected or could still develop a mild case if exposed to the virus.
If for any reason you catch it, you could still spread the virus. And that’s why it’s still important that you get tested.
What is a case pos t vaccination?
When a person becomes infected with coronavirus after being fully vaccinated, this is called a post-vaccination infection case.
These cases demonstrate a basic principle of infectious diseases, whether or not a person is infected depends on the balance between two factors: the intensity of exposure and immune competence .
The intensity of exposure is related to how close an uninfected person is to a highly infectious individual who shed the virus while talking and how long the two remain in contact.
Immune competence is about the body’s inherent protection against COVID-19. Individuals who are not vaccinated and have never been infected with coronavirus have no protection – this is a completely new virus after all – while people who are fully vaccinated will have much more protection.
According to the US Centers for Disease Control (CDC), as of April 30, 2021, 10,262 post-vaccination infections of SARS-CoV-2 had been detected in the United States and its territories.
These are usually asymptomatic or mildly symptomatic cases , and most do not require hospitalization .
Post-vaccination infections will continue and although these people are less likely to spread the coronavirus than individuals who are not vaccinated, they still can.
And what about the SARS-CoV-2 variants? Well, the world has been fortunate that mRNA vaccines in particular provide significant protection against all the major variants that have emerged thus far.
But it is perfectly possible that at any given moment a strain of coronavirus could mutate and partially or totally evade the protection of vaccines . This is another good reason to get tested if you feel bad.
As the pace of vaccinations increases and the number of daily cases falls in the US and other countries, it is also important to keep a close eye on the coronavirus.
Covid-19 testing allows authorities to keep track of how much virus is in a community, and positive test results can help quarantine people before they inadvertently spread the virus to others.
