Misleading: The seasonal flu and COVID-19 are both respiratory illnesses but there are key differences between the two that underpin differences in public health responses to both illnesses. For example, COVID-19 is deadlier and more likely to cause complications compared to the flu.
FULL CLAIM: Natural immunity is best for COVID-19; “Check out this clip of Dr. Fauci in 2004 talking about the STRENGTH of Natural Immunity.. Fast forward 18 years, what happened to this ‘science?!’ Why does Fauci continue to LIE to the American people?!”
In early April 2022, several social media posts shared a video clip of a 2004 Washington Journal interview of Anthony Fauci on the subject of the flu and the flu vaccine. During the interview, Fauci was asked if someone who got the flu still needs to get a flu vaccine. He replied that “If she got the flu for 14 days, she’s as protected as anybody can be because the best vaccination is to get infected yourself”. The full interview can be found on C-SPAN.
Some social media posts, such as this Facebook post from the political advocacy group FreedomWorks, implied that his remarks meant that infection-induced immunity for COVID-19 is also better than vaccination. The post also claimed that Fauci had been dishonest about infection-induced immunity: “Fast forward 18 years, what happened to this ‘science?!’ Why does Fauci continue to LIE to the American people?!” FreedomWorks followed up with another post, this time containing a meme quoting Fauci from the 2004 interview, which was interpreted by several users to mean that natural immunity is preferable to vaccination in the case of COVID-19 as well. This Facebook post by Young Americans for Liberty, and another by Tea Party Patriots, were also interpreted by several users in the same way.
However, the posts are inaccurate in suggesting that “the science” has been ignored. The fact that infection can generate immunity isn’t disputed by scientists, including Fauci. But one of the problems with infection-induced immunity, that vaccination doesn’t have, is that infection-induced immunity is unpredictable. Paul Offit, a pediatrician and professor of vaccinology at the University of Pennsylvania, told Health Feedback that both infection and vaccination can protect people from serious illness. But in the case of infection-induced immunity, the level of protection depends on the severity of the infection.
“If your initial illness with COVID is an asymptomatic infection or a mildly symptomatic infection, you may be less protected than if you’re vaccinated,” he explained. “But if you have a moderate or severe illness associated with COVID, you’re well-protected against severe illness upon subsequent exposure.”
He pointed out that “vaccination tends to protect more consistently [than infection], because you’re given a known dose of the virus.” On the flip side, immunity developed from infection is much less predictable because people receive variable doses of the virus.
A study of more than 1,700 people in Iceland also estimated that about 9% of infected people don’t have detectable levels of antibodies four months after infection.
Furthermore, infection-induced immunity is more dangerous, as it entails running the risks from illness, including organ damage and death. The Facebook posts didn’t acknowledge this fact.
Overall, natural immunity can protect people, but it’s less reliable because the level of protection depends on factors such as the amount of virus that caused the infection (infectious dose) and disease severity, which aren’t under our control. On the other hand, vaccine-induced immunity is uniform and robust thanks to the consistent dosage. Therefore, vaccine-induced immunity is more reliable and safer compared to infection-induced immunity. This is why public health officials continue to recommend vaccination over infection, even if people were previously infected. This Insight article by Health Feedback discusses the debate over vaccine-induced immunity and natural immunity in greater detail.
Another feature of these social media posts is the attempt to draw parallels between the flu and COVID-19, which do share several similarities. Both are respiratory illnesses that can produce the same symptoms. However, they both differ from each other in important ways, as explained by the U.S. Centers for Disease Control and Prevention, and these key differences are the reason why the public health response to each one is different. Therefore, extrapolating vaccine recommendations for flu to COVID-19 is misleading as it fails to account for these differences. It’s not the first time that misleading comparisons between the flu and COVID-19 have been made; Health Feedback documented and debunked several in the past, such as the inaccurate claim that flu and COVID-19 have the same case fatality rate.
COVID-19 is deadlier than the flu. A study done in France and published in December 2020 in The Lancet Respiratory Medicine found that COVID-19 was more likely than flu to cause complications and therefore more likely to kill. Another study on U.S. veterans showed similar trends, with COVID-19 being associated with a higher risk of damage to various organs as well as death. The UK charity Health Foundation analyzed mortality data for flu and COVID-19 and found that COVID-19 exacted a higher death toll:
“In a particularly bad flu year on average around 30,000 people in the UK die from flu and pneumonia, with a loss of around 250,000 life years. This is just a sixth of the life years lost to COVID-19.“
Figure 1. A comparison of years of life lost from the flu and COVID-19 among the elderly. Graph from The Health Foundation.
The answer to the question “Will COVID-19 protect against illness, especially severe illness, upon reexposure to the virus” is yes. Natural infection can also protect against serious illness, just like vaccination can protect serious illness. The difference is, it depends on the nature of your initial illness. In other words, if your initial illness with COVID is an asymptomatic infection or a mildly symptomatic infection, you may be less protected than if you’re vaccinated. But if you have a moderate or severe illness associated with COVID, you’re well-protected against severe illness upon subsequent exposure. So natural infection can protect. I think it’s fair to say though, that vaccination tends to protect more consistently, because you’re given a known dose of the virus. Because when you’re naturally infected, you’re essentially given variable doses of the virus. But when you get vaccinated, you get a known dose of the viral surface protein.
- 1 – Gudbjartsson et al. (2020) Humoral Immune Response to SARS-CoV-2 in Iceland. New England Journal of Medicine.
- 2 – Piroth et al. (2020) Comparison of the characteristics, morbidity, and mortality of COVID-19 and seasonal influenza: a nationwide, population-based retrospective cohort study. The Lancet Respiratory Medicine.
- 3 – Xie et al. (2020) Comparative evaluation of clinical manifestations and risk of death in patients admitted to hospital with covid-19 and seasonal influenza: cohort study. BMJ.