This article is part of TPM Cafe, TPM’s home for opinion and news analysis. It was originally published at The Conversation.
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.
What about the 3.6% without antibodies?
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. https://www.youtube.com/embed/fgmhm4IX-M8?wmode=transparent&start=0 Here’s how antibodies help your body fight against an invader like the coronavirus.
A clearer picture of a virus’s spread
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.
What does this statistic mean for future waves?
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. Read the original article.
FRIST!!! I am one of those with single source immunity - I’ve been vaccinated but managed to avoid the real thing. That said, I’m one of those that is in a bind on the vaccine front - I got vaccinated early on but proved allergic to the Pfizer mRNA vaccine, so I can’t have any more of those. I haven’t been boosted since 2021. I keep waiting for a new Novavax or similar vaccine that doesn’t use the same ingredients as Pfizer and Moderna, but, so far, no luck.
ETA No cats (I’m allergic to them) but here’s my Dad’s rescue dog.
Millions of Americans face similar issues making them absolutely dependent on the rest of us not acting like selfish children.
I have a family member who’s been battling cancer since the pandemic began: chemo, radiation, even clinical trials, for months on end. The cancer, along with the ravages of these therapies, devastate their immune system. Even a common cold virus could lead to hospitalization – or worse – let alone COVID.
And yet, everyone seems to think (as I’m sure you know only too well) that everyone is exactly like them. The idea that every family is different, with its own health needs and challenges, never even crosses their minds.
(Maskless strangers have confronted family members in public, demanding – demanding! – that they remove their masks, because “There’s no pandemic! It’s all a hoax! Sheeple!”)
It wasn’t until COVID that I fully appreciated the struggle faced by those for whom the ADA was passed. Most people, in their unbelievable fortune, just haven’t a clue that others might be less fortunate, in health, money, gender and color privilege, etc.
Sorry to hear it’s a genuine problem for you too, especially knowing how a selfish and petty minority (and a clueless majority) make it even more challenging.
Stay safe!
One individual (Individual One?) made this situation much worse than it would have been otherwise. It’s too bad he can’t be prosecuted for that.
This is science. Science & research & study is good … vital in fact!
This speaks to a colossal piece of malevolent Luddite level ignorant destructiveness advances by theformer president - back in the days of grappling with defining & characterizing COVID-19 …back when it was known that it was entirely possible to have sub-clinical cases … and so the true incidence & prevalence (mighty damn important for grappling with communicable diseases) as an unknown!
Yeah … it was at this point that Trump barfed out one of the STUPIDIST and most reckless things of his regime … “Don’t Test - because if you keep testing … you find more positive cases”
Truly an imbecile - a dangerous, willfully stupid evil opportunistic self-serving psychopath.
Wife & I have had the Pvizer vaccine with all the boosters available; no ill effects. Agree wholeheartedly that the former President’s response to the pandemic was unspeakable. Given that, because today is Saturday, because I’ve had 3 cups of coffee, and because I’m relaxing on the patio enjoying nearly the last cool morning before summer in all its rage hits sunny Mesa, I find myself musing that it would be good for all of us were someone with talent to compose a Gilbert & Sullivan-ish musical comedy, similar to Pirates of Penzance, about the entire Trump debacle. We really need to laugh. And Mr. Trump really must hear us turning his farcical tragedy into a comedy.