Antibodies to SARS-CoV-2, the virus that causes COVID-19, were present in the blood of 96.4% of Americans over the age of 16 by September 2022. That’s according to a serosurvey – an analysis testing for the presence of these immune defense molecules – conducted on samples from blood donors.
A serosurvey like this one helps researchers estimate how many people have been exposed to any part of the coronavirus, whether via vaccination or infection. Both can trigger the generation of antibodies to SARS-CoV-2. And by identifying which kind of antibodies someone has in their blood, researchers can break down the 96.4% into different types of immunity: infection-derived, vaccine-derived and hybrid.
COVID-19 vaccines used in the United States are based on only one part of the virus – the spike, or S, protein. Researchers can tell that a person has been vaccinated and has not been infected if their blood has only anti-S antibodies that target that spike protein. If someone has anti-N antibodies, which target the virus’s nucleocapsid protein, it’s a sign that they’ve been infected by SARS-CoV-2. To reliably identify someone with hybrid immunity, a researcher would need to match someone who has anti-N antibodies to an official vaccination database.
Immunologists know that antibody levels decrease in the months after a COVID-19 infection or vaccination, and this is true for many pathogens. It’s possible some people did have antibodies at one point, but they’re no longer detectable. And not every infection leads to a detectable antibody response, particularly if the case was mild or asymptomatic.
Another factor is the accuracy of the antibody test. No test is perfect, so a small percentage of people who truly have antibodies might come up negative.
Together, these considerations mean that the 96.4% number is likely an underestimate. It seems reasonable to conclude that almost no one in this population has neither been infected by SARS-CoV-2 nor received a COVID-19 vaccine.
Serosurveys are useful for understanding how likely different types of people – of varying ages or races, for example – were to have been infected. For this purpose, a serosurvey can be much more reliable than using data on people who received a positive PCR test, or who report having had a positive rapid antigen test, because getting a positive test is heavily influenced by access to care, health care behavior and how severe your illness is. These are sources of what is called bias.
This bias has two effects: It leads to large underestimation of the proportion of the overall population infected, and it can lead to spurious differences between groups. For example, people with mild symptoms are less likely to get tested and are also likely to be younger. Researchers might draw the wrong conclusion that because they’re not getting tested these people aren’t actually catching the virus.
Looking at antibodies as a marker of infection is not biased by such behavioral factors. Many serosurveys, including ones that we worked on in Chennai, India, and Salvador, Brazil, found similar or even higher seroprevalence in children compared with young adults, contradicting an early narrative that children were less susceptible to the virus. Instead, our results suggested that infections in children were less likely to be detected.
Antibodies are not just a marker of previous infection; part of their job is to help prevent future infection with the same pathogen. So, serosurveys can be used to understand levels of immunity in the population.
For some diseases, like measles, immunity is essentially lifelong, and having antibodies means you are protected. However, for SARS-CoV-2 this is not the case, because the virus has continually evolved new variants that are able to reinfect people despite their antibodies.
Nevertheless, many studies have shown that individuals with hybrid immunity will be more protected against future infection and variants than those with vaccine- or infection-derived immunity alone. It may be useful to know the proportion of the population with single-source immunity in order to target certain groups with vaccination campaigns.
This article is republished from The Conversation under a Creative Commons license.
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MamaMia
So if we were exposed to someone with COVID, we have the antibodies to fight it off? Or if we were vaccinated against COVID, we have the antibodies? Early on, Mayor Nelson provided people with free testing at a drive thru event at the VFW in Apopka. The fire department paramedics gave use the blood tests. It was to determine if any person had the COVID antibody in their bodies. Every person that day, in line, including my husband, and me tested negative. Later, the mayor was informed, that the tests may have been compromised, invalid, inaccurate or whatever it was stated. I'll be darned if people didn't start attacking the mayor over it. He didn't manufacture the tests. Just ridiculous. This is the mentality of people in this town. When I donate blood, they label mine rare. I do not have a rare blood type, but have rare antibodies in my blood. It is not COVID related. I don't know what it is. I was told I could find out at the big blood bank in Orlando, if I go there Once, the blood bank asked me if I would come in, and donate for a person who needed the antibodies from my blood, who was in the hospital, and I went to the local blood bank here and donated my blood, hoping to help that person in the hospital.
Monday, June 19, 2023 Report this
MamaMia
You know, there sure was not much news nationally about the Unabomber's death, or about Pat Robertson's death either. Two famous men, but plenty about Trump lately. It really will be ridiculous if we have a US president, a commander in chief, serve behind prison bars.
Monday, June 19, 2023 Report this
maylinna
All the Mayor’s SHEEP waited in that line for fake tests. He bought them fake tests from another sheep that donated to his campaign. The Mayor blew taxpayer dollars on them tests.
Monday, June 19, 2023 Report this
MamaMia
Maylinna, or in reality, Mr Apopka Mole, I am not a sheep FYI. Also, it wasn't just "so-called sheep" getting the tests in line, as I saw one of our very own Apopka retired paramedics getting the test, to see if he had any COVID antibodies in his body. I don't have knowledge of where the mayor got the tests from, probably a government entity, state or federal, but I am certain 100 % your assertion is pure bologna, as he certainly didn't aquire those tests from a sheep.....baa baa baa baa.
Tuesday, June 20, 2023 Report this
maylinna
https://youtu.be/xK1J0U6NaAY
Just look at how this SCREAMS USED CAR SALESMAN sales pitch. The Mayor bought the tests from his friend, NOT a government agency. Wasted taxpayer dollars again!
Tuesday, June 20, 2023 Report this
MamaMia
Maylinna, Mr. Mole, I am not going to your link. Wherever the mayor got the antibody tests from for our citizens to be tested, he got them in good faith to use, and did not know that they could possibly be inaccurate. You blantantly call these tests he had administered "fake", but the truth is, they were not fake, but legitimate Covid antibody tests. These Apopka tests given were not tested for the accuracy later, but what was said was, they could have been accurate, or may not of been accurate, and that is because so many of the antibody COVID tests are inaccurate. Many of the COVID at home tests to see if you have COVID are too.
Tuesday, June 20, 2023 Report this
maylinna
Yo mama, for you and the Kernal of the Nators CULT.
A lie can travel halfway around the world while the truth is putting on its shoes. There are always four sides to a story: your side, their side, the truth and what really happened. A lie told often enough becomes the truth. If you tell the truth you don't have to remember anything.
Tuesday, June 20, 2023 Report this
maylinna
*Mayors
Tuesday, June 20, 2023 Report this
maylinna
*Kernel
Tuesday, June 20, 2023 Report this
MamaMia
Maylinna, or Mr. Apopka Mole,. So this is your reasoning, that if a lie is told often enough, it becomes truth. Really Mole? Clearly this you believe, because your mode of operation is that, lies, lies, and more repeated lies by you, over and over hoping you get someone to believe you. Well, it won't be me.
Tuesday, June 20, 2023 Report this