Lack of context: The claim that infection provides stronger immunity than vaccination is based on the proportion of infections among vaccinated and previously infected individuals. However, this comparison is meaningless because it doesn’t consider important factors, such as the severity of the disease or the lower total number of infections compared to pre-vaccination waves.
FULL CLAIM: “Natural Immunity is far superior [to COVID-19 vaccines], with 1% experiencing re-infection while 40% of new cases were previously vaccinated”
REVIEW
On 20 December 2020, Israel launched the fastest COVID-19 vaccination campaign seen in the world so far. In only two months, half of the country’s population had received at least one dose of the Pfizer-BioNTech COVID-19 vaccine. This also enabled Israel to provide the first data about the real-world effectiveness of COVID-19 vaccines.
This tweet by Del Bigtree, who has shared vaccine misinformation in the past, claimed that Israel’s data showed immunity from infection to be “far superior” to that of COVID-19 vaccines. Bigtree’s tweet contained a link to an article by Israel National News, claiming that vaccinated people were 6.72 times more likely to get infected than previously infected individuals. Iterations of this claim were shared on media outlets and social media platforms, including Facebook and Twitter (see examples here and here).
Bigtree’s claim is highly misleading because it disregards the primary benefit of vaccines, which is providing immunity without exposing the person to the risks associated with the disease. In addition, simply comparing the number of COVID-19 cases in previously infected and vaccinated individuals isn’t enough to determine which group is better protected against the disease, as we explain below.
Vaccination is the safest way of acquiring immunity because it avoids the risks associated with infection
As the Vaccine Education Center of the Children’s Hospital of Philadelphia explained, the fundamental difference is “the price paid for immunity”. The main benefit of vaccines over infection is that they confer immunity to a disease without requiring the person to run the risks of being ill and the complications arising from illness, which Health Feedback also explained earlier in this review.
COVID-19 can cause a wide range of clinical outcomes, from mild symptoms to severe disease and death. Although most COVID-19 cases are mild, SARS-CoV-2 is a highly contagious virus. Therefore, it is still capable of causing many deaths simply by infecting a large number of people. Indeed, COVID-19 has already caused more than 4.2 million deaths worldwide.
Among those who survive, some show permanent lung and heart damage, as well as neurological issues after recovery, as Health Feedback explained in this review[1,2]. Others develop post-intensive care syndrome (PICS) as a result of long hospitalizations and ICU stays. This condition involves physical, cognitive, and psychological problems that generally require rehabilitation.
Finally, about one-third of the recovered patients develop long COVID[3,4]. This condition involves persistent health problems, including difficulty breathing, fatigue, cognitive problems, and joint and muscle pain[3]. Long COVID can even occur in patients who only had mild disease and can last for months[4,5].
Given the potentially serious complications that COVID-19 can cause, choosing infection over vaccination is like choosing to swim across a shark-infested sea (the disease) instead of using the bridge (the vaccine) because one fears the bridge collapsing, even though being eaten by sharks is far more likely than the bridge collapsing. Several studies in real-world conditions show that mRNA COVID-19 vaccines are over 80% effective at preventing infection and more than 94% effective against hospitalization and death. On the whole, it is much safer to get the COVID-19 vaccines than not to.
COVID-19 vaccines retain a high level of effectiveness against severe COVID-19 caused by the Delta variant
The spreading of the more contagious Delta variant in Israel is causing a COVID-19 surge in the country. The article in Israel National News reported more than 7,700 new confirmed COVID-19 cases in Israel since May 2021, citing data from the Israeli Ministry of Health. Over 3,000 (40%) of them were among fully vaccinated people, whereas only 72 (1%) occurred in people who had recovered from a previous infection. The article then calculated the infection rate among the total number of recovered (835,792) and vaccinated (5,193,499) people in Israel, concluding that vaccinated people are 6.72 times more likely to get infected:
Proportion of infections in fully vaccinated people:
3,000×100/5,193,499 = 0.0578%
Proportion of infections in previously infected people:
72×100/835,792=0.0086%
The article in Israel National News is misleading because this comparison between vaccinated and recovered patients is meaningless without considering other important factors. First, the fact that vaccinated people account for 56% of new COVID-19 cases in Israel as of 8 August 2021, isn’t a sign that COVID-19 vaccines are ineffective. Not only are they effective, but as explained above, they provide immunity in a safer way than infection. Simply comparing the strength of the immunity induced by vaccination and infection without additional context suggests that both strategies are equivalent in terms of the risk-benefit ratio, which is incorrect.
Because COVID-19 vaccines aren’t 100% effective, a small proportion of vaccinated people will still get infected and develop the disease. As the number of vaccinated people increases in a population, so will the proportion of infections in this group. In a 100% vaccinated population, all deaths would occur in vaccinated persons. However, the proportion of infections and deaths would be much lower than in a 100% unvaccinated population. At the time of this review’s writing, Israel has fully vaccinated 62% of its population, or 85% of all adults. Despite the Delta variant surge, the country has at least five times fewer hospitalizations and deaths now than in February 2021, indicating that COVID-19 vaccines are effective in preventing severe COVID-19 and death.
Second, it is difficult to accurately estimate the infection rate among vaccinated and previously infected individuals because infections in these groups of people tend to be mild. Therefore, many of such infections are likely to go undetected[6,7]. Also, there may be differences in healthcare-seeking behaviour between vaccinated and unvaccinated people, which may contribute to different testing and detection rates between the two groups. Unless the whole population was periodically tested for COVID-19, it is highly challenging to determine the total number of infections in each group.
Finally, Israel’s public data about the vaccination status of infected individuals are incomplete, which might lead us to incorrect interpretations. For example, we don’t know the proportion of previously infected individuals who were also vaccinated. This is an important consideration, given that some studies indicate that previously infected individuals who are also vaccinated have a stronger immunity.
For example, one study published in August 2021 showed that vaccination with one of the COVID-19 vaccines authorized for emergency use in the U.S. reduced the likelihood of reinfection 2.34 times in individuals who had a previous infection[8]. Therefore, if the majority of previously infected people were also vaccinated, this may explain a lower rate of infection in this group.
The headline of the Israel National News’ article, “natural infection vs vaccination: which gives more protection?” suggested a false dichotomy between immunity from previous infection and COVID-19 vaccines: that is, you can have infection-mediated immunity OR vaccine-mediated immunity, but not both. The results from this study illustrate that natural immunity and vaccination are NOT mutually exclusive and that individuals who recovered from previous infection can also benefit from COVID-19 vaccines.
The Israel National News’ article didn’t account for all these factors, as well as the fact that one of the most important considerations for evaluating vaccine efficacy is not only how well the vaccine reduces infection rate, but also how well it prevents serious disease and death.
Despite the Delta variant, real-world studies in Israel show that the Pfizer-BioNTech COVID-19 vaccine is still 64% effective against both infection and symptomatic disease, and over 93% effective against serious illness and hospitalization[9]. The result of this is that the number of cases, hospitalizations, and particularly deaths in Israel is now much lower than in previous waves (see Figure 1). However, the data reported in Israel National News focused exclusively on infections. Its analysis thus didn’t consider potential differences in the rate of severe COVID-19 and death between vaccinated people and previously infected people.
Figure 1. Daily new number of COVID-19 cases (upper left graph), hospitalizations (upper right graph), and deaths (lower graph) in Israel between 26 February 2020 and 8 August 2021. Daily new confirmed cases and deaths are presented as the rolling 7-day average. Data and image from Our World in Data.
While immunity from infection is generally more robust than that from vaccination, this isn’t always the case. This article in The Conversation by Jennifer Grier, an assistant professor of immunology at the University of South Carolina, explained that mRNA COVID-19 vaccines induce a stronger immune response in people who never had the disease than that observed in unvaccinated people who recovered from infection[10].
Immunity from COVID-19 vaccines is also more consistent than from infection, which varies greatly between different individuals, depending on factors such as age and disease severity[11,12]. Knowledge about natural and vaccine-induced immunity is still evolving, and future studies will allow researchers to make long-term comparisons between both.
Conclusion
Israel is evidence that COVID-19 vaccines are effective in controlling the pandemic in the real world. Vaccination has reduced the number of COVID-19 cases, hospitalizations, and deaths in the country, even in the face of the more contagious Delta variant. Posts comparing the rate of infection among vaccinated people and previously infected individuals lack important context and are misleading. Such comparison ignores the fact that natural immunity implies exposure to the disease and its associated risks. For this reason, COVID-19 vaccines are the safest way of acquiring immunity, regardless of whether the response they generate is or not superior to that induced by infection.
This review was updated to provide readers with a more precise explanation as to why the article in Israel National News is missing context. The changes affect some of the paragraphs discussing the data from the Israeli Ministry of Health. Reference 10 was added to address a reader’s comment about the strength of the immunity induced by vaccination.
REFERENCES
- 1 – Nishiga et al. (2020) COVID-19 and cardiovascular disease: from basic mechanisms to clinical perspectives. Nature Reviews Cardiology.
- 2 – Zarrilli et al. (2021) The Immunopathological and Histological Landscape of COVID-19-Mediated Lung Injury. International Journal of Molecular Sciences.
- 3 – Logue et al. (2021) Sequelae in Adults at 6 Months After COVID-19 Infection. Infectious Diseases.
- 4 – Jacobson et al. (2021) Patients With Uncomplicated Coronavirus Disease 2019 (COVID-19) Have Long-Term Persistent Symptoms and Functional Impairment Similar to Patients with Severe COVID-19: A Cautionary Tale During a Global Pandemic. Clinical Infectious Diseases.
- 5 – Blomberg et al. (2021) Long COVID in a prospective cohort of home-isolated patients. Nature Medicine.
- 6 – Thompson et al. (2021) Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers — Eight U.S. Locations, December 2020–March 2021. Morbidity and Mortality Weekly Report.
- 7 – Thompson et al. (2021) Prevention and Attenuation of Covid-19 with the BNT162b2 and mRNA-1273 Vaccines. New England Journal of Medicine.
- 8 – Cavanaugh et al. (2021) Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination — Kentucky, May–June 2021. Morbidity and Mortality Weekly Report.
- 9 – Bergwerk et al. (2021) Covid-19 Breakthrough Infections in Vaccinated Health Care Workers. New England Journal of Medicine.
- 10 – Jackson et al. (2020) An mRNA Vaccine against SARS-CoV-2 — Preliminary Report. New England Journal of Medicine.
- 11 – Anderson et al. (2020) Safety and Immunogenicity of SARS-CoV-2 mRNA-1273 Vaccine in Older Adults. New England Journal of Medicine.
- 12 – Widge et al. (2021) Durability of Responses after SARS-CoV-2 mRNA-1273 Vaccination. New England Journal of Medicine.
