CDC data didn’t show COVID-19 vaccines increase risk of hospitalization, contrary to claim by The Epoch Times
COVID-19 bivalent vaccines were developed to provide protection against the original form of SARS-CoV-2 as well as the Omicron variant. The U.S. Centers for Diseases Control and Prevention data showed that the bivalent booster had a limited and waning effectiveness against hospitalization due to infection by the dominant Omicron variant lineage called XBB. However, they are effective at protecting from severe forms of the disease in the case of infection by other Omicron lineages such as BQ.1 or BA.4/5.
Inadequate support: The claim hinges on statistical estimates of vaccine effectiveness. Yet, the claim failed to take into consideration the large uncertainty that surrounds these estimates. This means that it isn’t possible with this data to conclude if vaccines increase or decrease the risk of hospitalization.
Misrepresents source: The claim cites a study from Irrgang and colleagues as supporting evidence. However, their work showed the opposite: repeated vaccination increased the neutralization of the virus SARS-CoV-2. Furthermore, the study authors publicly contradicted the claim.
The narrative that COVID-19 vaccines increase the risk of getting sick with COVID-19 has resurfaced many times since the start of the vaccination campaign in late 2020. Health Feedback explained previously on multiple occasions that claims feeding this narrative are inaccurate or misleading and based on flawed analysis of epidemiological data.
The same narrative resurfaced in June 2023, with The Epoch Times claiming that “COVID-19 vaccine effectiveness against hospitalization turned negative over time”, in other words, people who were vaccinated against COVID-19 were more likely to be hospitalized. As on previous occasions, this claim is unsubstantiated as it relies on a misleading interpretation of epidemiological data. We explain why below.
CDC study is inconclusive on effect of bivalent vaccines on hospitalization
On 15 June 2023, the Epoch Times reported on a presentation by U.S. Centers for Diseases Control and Prevention (CDC) epidemiologist Ruth Link-Gelles at the U.S. Food and Drug Administration’s (FDA) 182nd Meeting of Vaccines and Related Biological Products Advisory Committee.
Link-Gelles presented data on the effectiveness of the mRNA bivalent COVID-19 vaccines in preventing COVID-19 hospitalization in case of infection with several Omicron lineages. Vaccine effectiveness (VE) measures the ability of the vaccine to reduce a specific outcome, such as infection, hospitalization or death. A positive VE means that the vaccine effectively lowers the risk of that outcome. In theory, a negative VE would mean that the vaccine increases that risk.
Link-Gelles reported that there was an average vaccine effectiveness (VE) of minus eight percent against hospitalization under a specific set of conditions: when using data from the IVY vaccine surveillance network; when the hospitalization occurred at the time when the Omicron lineage XBB was predominant (23 January 2023 to 24 May 2023); and when hospitalized people had received their bivalent booster shot more than 90 days earlier. It is this finding that the Epoch Times used to support its claim.
It’s important to keep in mind that the average VE was positive under all other conditions except for the above: when the predominant Omicron lineage was BA.4/5 (8 September – 13 November 2022), or BQ.1 (14 November 2022 to 22 January 2023), and when the data were obtained from another CDC vaccine surveillance network, the VISION network.
However, the article failed to take into consideration some important caveats. First, Link-Gelles reported the average VE together with its 95% Confidence Interval (CI). While the average VE is indeed -8%, the 95% CI intervals ranged from -44% to +19%.
To understand why this is important, we must first understand that the VE data were obtained from a sample of the population, not the entire vaccinated population in the U.S. Therefore, the calculated VE is in fact an estimate of the true VE that we would find if we were able to include the entire population in the analysis.
A 95% CI tells us that we are 95% confident that this interval contains that true, unknown VE. More specifically, it means that if we were to repeat the same study 100 times, each time calculating a new 95% CI, the true VE would be included in those CIs 95% of the time.
Circling back to the 95% CI reported by Link-Gelles, we can say that we’re 95% confident that the actual VE is somewhere between -44% and +19%. In other words, this piece of data alone cannot help us to conclude if the VE is negative or positive. But we can turn to other studies investigating bivalent vaccine effectiveness to gain a better understanding.
For instance, data obtained by the CDC from the VISION Network found a positive VE against hospitalization, as mentioned earlier.
Researchers from the University of North Carolina also reported positive, albeit low, VE against hospitalization, even when the XBB Omicron lineage was predominant.
Hence, the Epoch Times’ claim is based solely on a single VE estimate, while excluding other estimates that showed the opposite effect.
There are also other caveats to the VE estimates presented at the meeting. The CDC presentation warned that “For estimates of absolute vaccine effectiveness, if unvaccinated are meaningfully different from vaccinated individuals (e.g., by COVID-19 risk factors), estimates may be biased”.
In other words, the absolute VE presented by the CDC cannot be used as-is to draw definitive conclusions. This is because there might be differences between the vaccinated and unvaccinated populations—unrelated to vaccination—that influence their risk of developing severe COVID-19 that could affect the VE calculation.
Antibody study doesn’t suggest that vaccines weaken the immune system
To support their claim, The Epoch Times also cited a scientific study allegedly showing that repeated vaccination “weakens immune systems, potentially making people susceptible to life-threatening conditions such as cancer”.
The Epoch Times indirectly referred to a study by Irrgang and colleagues that reported a change in the anti-Spike antibodies produced after a third dose of mRNA vaccine. It did so by linking to an earlier article, also by the same author, which cited two scientific publications. One is the study by Irrgang and colleagues. The other is a review that only cited Irrgang et al. as supporting evidence for the claim that the change could lead to immune tolerance. We can thus deduce that the basis for this claim rests mainly on this study. However, the Epoch Times’ account of the study’s results is misleading.
Irrgang et al. observed an increase in a specific class of antibodies called IgG4 after the second and third vaccine doses.
Part of the claim may be related to how the IgG4 class of antibodies is associated with anti-inflammatory properties and lacks certain immune functions conventionally associated with antibodies.
However, there’s no evidence so far that indicates the increase in IgG4 class antibodies following mRNA vaccination weakens the immune response. Kilian Schober, an immunologist at the Universitätsklinikum Erlangen and a co-author of the study by Irrgang et al., wrote on Twitter that such a view was “certainly too simplistic”, pointing out that “mRNA vaccines have saved millions of lives”.
Schober emphasized that IgG4 antibodies still retain the ability to bind to the Spike protein. In fact, Irrgang and colleagues observed an improvement in the ability of antibodies to bind Spike and an improved antibody-mediated virus neutralization after the booster dose.
Shiv Pillai, a professor of medicine at Harvard Medical School who was not involved in the research, explained that the ability of antibodies to neutralize their target is “the most rigorous correlate of immune protection after vaccination”. He also suggested that anti-Spike IgG4 antibodies may even bind more strongly to their target. Pillai concluded that “in practical terms, [IgG4 antibodies] are unlikely to compromise immunity in vaccinated patients at this time”.
Since the beginning of the vaccination campaign, numerous studies showed that vaccines effectively reduced the risks of hospitalizations due to COVID-19[2,7,8]. One study estimated that around 20 million deaths to COVID-19 were averted globally by vaccinations in the first year of the rollout.
In summary, the Epoch Times’ coverage of the presentation is misleading. CDC data from June 2023 don’t show that a higher number of COVID-19 vaccines increase the risk of hospitalization. Most VE estimates from the CDC actually point toward a reduction in hospitalization risk. Statistical uncertainty and possible bias in the calculation of absolute VE preclude definitive conclusions. Studies on the production of antibodies in vaccinated people show that booster doses increase the neutralization of SARS-CoV-2. While a study did show an increase in IgG4 antibodies after mRNA vaccination, it didn’t show that this interfered with virus neutralization.
UPDATE (4 July 2023):
Additional information was added to the seventeenth paragraph to explain how the Epoch Times article’s misleading interpretation of the study by Irrgang et al. was used to support its claim.
- 1 – Tan & Tan (2010) The Correct Interpretation of Confidence Intervals. Proceedings of Singapore Healthcare.
- 2 – Link-Gelles et al. (2023) Estimates of Bivalent mRNA Vaccine Durability in Preventing COVID-19–Associated Hospitalization and Critical Illness Among Adults with and Without Immunocompromising Conditions — VISION Network, September 2022–April 2023. Morbidity and Mortality Weekly Report.
- 3 – Yin et al. (2023) Durability of Bivalent Boosters against Omicron Subvariants. The New England Journal of Medicine.
- 4 – Irrgang et al. (2023) Class switch toward noninflammatory, spike-specific IgG4 antibodies after repeated SARS-CoV-2 mRNA vaccination. Science Immunology.
- 5 – Uversky et al. (2023) IgG4 Antibodies Induced by Repeated Vaccination May Generate Immune Tolerance to the SARS-CoV-2 Spike Protein. Vaccines.
- 6 – Rispens & Huijbers (2023) The unique properties of IgG4 and its roles in health and disease. Nature review immunology.
- 7 – Havers et al. (2022) COVID-19-Associated Hospitalizations Among Vaccinated and Unvaccinated Adults 18 Years or Older in 13 US States, January 2021 to April 2022. JAMA Internal Medicine.
- 8 – Link-Gelles et al. (2023) Estimation of COVID-19 mRNA Vaccine Effectiveness and COVID-19 Illness and Severity by Vaccination Status During Omicron BA.4 and BA.5 Sublineage Periods. JAMA Network Open.
- 9 – Watson et al. (2022) Global impact of the first year of COVID-19 vaccination: a mathematical modeling study. The Lancet infectious diseases.