Inadequate support: The claim that everyone who was infected is now immune isn’t supported by scientific evidence. For example, infection with one strain doesn’t guarantee protection from another strain. In fact, there’s evidence that the Delta variant is associated with a higher risk of reinfection.
FULL CLAIM: “The CDC Finally Admits a Massive Number of Americans Have ‘Natural Immunity’: 146.6 Million People”; “natural immunity is superior protection against Covid-19 than vaccinated immunity”; “The CDC reports ‘Covid-related deaths,’ and not deaths caused by Covid-19. That is because 94% of Covid-related deaths had serious underlying medical conditions, such as heart disease, stroke, and diabetes”
REVIEW
An article published by Becker News in mid-November 2021, written by former Fox News writer Kyle Becker, claimed in its headline that “The CDC Finally Admits a Massive Number of Americans Have ‘Natural Immunity’: 146.6 Million People”. In addition, the article also claimed that “natural immunity is superior protection against Covid-19 than vaccinated immunity” and that 94% of COVID-19 deaths aren’t actually caused by COVID-19 because the people who died had comorbidities. Becker News has been classified as a questionable source by Media Bias/Fact Check for its publication of conspiracy theories and inaccurate information. The article received more than 2,200 engagements on Facebook, according to social media analytics tool CrowdTangle.
The article rehashed a claim from August 2020 that COVID-19 deaths involving people with underlying health conditions (comorbidities) weren’t actually caused by COVID-19. As explained by Health Feedback here and here, this is false and stems from a misunderstanding of what a cause of death and a comorbidity is. A cause of death is the illness that triggers the clinical chain of events that results in death. A comorbidity is a condition or disease that lowers a person’ overall state of health and makes them more susceptible to other illnesses. One example in the context of COVID-19 is asthma.
But a comorbidity doesn’t always lead to death. In fact, many people with asthma live out a normal lifespan. Therefore, COVID-19 deaths in people with comorbidities are still caused by COVID-19, because a person with a comorbidity would still be alive if they hadn’t developed COVID-19.
It’s also important to keep in mind that not all comorbidities recorded for 94% of COVID-19 deaths were pre-existing conditions unrelated to COVID-19, like heart disease, stroke, and diabetes. As Johns Hopkins epidemiologist Justin Lessler explained in this article, comorbidities can also arise as a result of COVID-19 itself, like respiratory failure.
The article’s claim that 146.6 million people in the U.S. have “natural immunity”, or infection-induced immunity, is based on a figure reported by the U.S. Centers for Disease Control and Prevention (CDC) representing the estimated total number of SARS-CoV-2 infections. That number stood at 146.6 million at the time of this review’s publication. Becker didn’t define what he meant by immunity, although the word is defined by Merriam-Webster as protection from disease.
Based on that definition, Becker’s assumption isn’t supported by scientific evidence for a few reasons. Firstly, we know that a certain proportion of previously infected people become reinfected, based on scientific studies[1-3]. This means that not everyone who was previously infected develops immunity to disease. Studies on reinfection that ended before the Delta strain became dominant worldwide found that reinfections were uncommon. One study conducted in Ohio and Florida reported that among 8,845 people who were infected, 62 become reinfected (0.7%); among these 62, 31 showed symptoms of illness[2]. Another study in Lombardy, Italy, reported that five people were reinfected among 1,547 COVID-19 patients (0.3%)[3].
But the emergence of virus variants like Delta significantly changed the game. For example, the Delta variant is more infectious than the original strain—data from the U.K. in November 2021 provided some evidence that the Delta variant is more likely to cause reinfection than other strains of SARS-CoV-2. This also suggests that immunity developed against one strain may not always protect as well against another.
Furthermore, there is also scientific evidence suggesting that immunity wanes over time, at least based on studies that track the amount of antibodies in blood over time. However, antibody levels are only one way of determining protection; other components of the immune system, such as T cells, also play an important role in immunity against viral infections as discussed by Health Feedback here. Since the factors that determine protection from disease, which scientists call “correlates of protection”, are still unclear, it’s unknown if antibody level alone are sufficient for establishing immunity.
It also isn’t true that “a staggering 146.6 million people have been infected by the Sars-CoV-2 virus and have survived it”, as Becker claimed. That would mean that everyone who was infected survived, but we know that isn’t true, as COVID-19 doesn’t have a 100% survival rate. In fact, the New York Times reported more than 700,000 COVID-19 deaths in the U.S. in early October 2021.
The article’s claim that “natural immunity is superior protection against Covid-19 than vaccinated immunity” rests on two studies, one preprint by scientists in Israel[4] and a published study by scientists in the U.S.[5]. The claim overstates scientific confidence for the first study and misrepresents the second.
While the study in Israel reported fewer infections in people who were previously infected compared to vaccinated people, the study was also affected by various biases, such as selection bias and survivorship bias. The study’s weaknesses were explained in this discussion led by James Lawler, an expert in infectious diseases and associate professor at the University of Nebraska, as part of the university’s weekly meetings with local and state public health representatives.
For example, Lawler pointed out that the vaccinated group in the study comprised more people who were in poorer health, such as people with cancer (selection bias). This is expected, given that COVID-19 vaccination campaigns in general prioritized high-risk groups like people in poorer health. On top of an overrepresentation of high-risk people in the vaccinated group, the study’s design meant that it left out unvaccinated people who got COVID-19 and died (survivorship bias). In short, the unvaccinated and vaccinated groups differ in many ways that are unrelated to their vaccination status, such that a comparison of the two may not provide meaningful information.
On the other hand, the second study examined antibodies in vaccinated people and compared the antibodies’ ability to neutralize virus variants (block infection) between people who were and weren’t previously infected. It concluded that previously infected people who were also vaccinated developed antibodies that were more capable of neutralizing variants compared to vaccinated people who weren’t infected before. The study didn’t include unvaccinated people who were previously infected. Claiming that this study showed infection-induced immunity to be better than vaccine-induced immunity is inaccurate and misleading, as it also involved vaccine-induced immunity.
Health Feedback discussed the debate surrounding infection-induced and vaccine-induced immunity in this Insight article, and explained why the benefit-risk profile of vaccine-induced immunity is more favorable than that of infection-induced immunity.
REFERENCES
- 1 – Cavanaugh et al. (2021) Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination — Kentucky, May–June 2021. Mortality and Morbidity Weekly Report.
- 2 – Sheehan et al. (2021) Reinfection Rates Among Patients Who Previously Tested Positive for Coronavirus Disease 2019: A Retrospective Cohort Study. Clinical Infectious Diseases.
- 3 – Vitale et al. (2021) Assessment of SARS-CoV-2 Reinfection 1 Year After Primary Infection in a Population in Lombardy, Italy. JAMA Internal Medicine.
- 4 – Gazit et al. (2021) Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections. medRxiv. [Note: This is a preprint that has not yet been peer-reviewed at the time of this review’s publication.]
- 5 – Cho et al. (2021) Anti-SARS-CoV-2 receptor-binding domain antibody evolution after mRNA vaccination. Nature.
