Vaccinated People Not More Susceptible to COVID-19 Than Unvaccinated
Q. Are vaccinated and boosted people more susceptible to infection or disease with the omicron variant than unvaccinated people?
A. No. Getting vaccinated increases your protection against COVID-19. Sometimes, certain raw data can suggest otherwise, but that information cannot be used to determine how well a vaccine works.
FULL QUESTION
Are fully vaccinated and boosted people more likely to get the Omicron strain of the virus?
Did Walgreens state that vaccinated are more likely to get covid and get it worse than un vaccinated people?
A friend of mine posted this from the gateway pundit and I was checking on its legitimacy. Below is the subject line for the article. “Walgreens Reveals Unvaccinated Have the Lowest Positivity Rate for COVID — Triple and Double Vaxxed Groups Have the Worst Rate”
FULL ANSWER
In recent weeks, we’ve received several questions about whether people who are vaccinated are more susceptible to COVID-19 than those who are unvaccinated, particularly against the omicron variant.
One such question came from a reader who wondered whether Walgreens had said vaccinated people were at higher risk. Another asked about a misleading article from the conservative news site the Gateway Pundit, which was also about Walgreens, while others have made no mention of the pharmacy chain.
A May Walgreens report did say that in early 2022, unvaccinated people getting tested for COVID-19 at the company’s pharmacies had a lower test positivity rate than those who had received at least one COVID-19 vaccine — a reversal from what was observed prior to the omicron variant.
But, as we’ll explain, that doesn’t mean that the vaccine is making people more susceptible. On the contrary, the report specifically notes that unvaccinated people were more likely to report having had COVID-19 before, and among those with a previous bout of COVID-19, “unvaccinated patients were significantly more likely to test positive than vaccinated patients.”
In the Walgreens case and in others, raw data can be misleading — a phenomenon that has been exploited by dubious websites that cherry-pick data points to argue that the unvaccinated are somehow better off than those who have opted for the shots. A substantial body of evidence shows that that is false: getting vaccinated increases — not lowers — your protection against the coronavirus.
Vaccine Protection Against Omicron
First, it’s true that people who have been vaccinated or boosted are more susceptible to becoming infected with the omicron variant than they were to past variants. The variant, which has been the dominant variant in the U.S. since the winter and now comprises several different subvariants, is more transmissible and more immune evasive. This has led to a surge of reinfections and infections in people who are vaccinated. In that sense, vaccinated people are at higher risk than they were before. But there’s no evidence they’re more likely to contract the virus than a similar person who is unvaccinated.
Multiple studies indicate the vaccinated or boosted are afforded at least some temporary protection against omicron infection, albeit at a reduced level compared with previous variants.
A study of patients in Southern California, for instance, found that two doses of the Moderna vaccine reduced the risk of omicron infection by 44% in the first three months, compared with 80% for the delta variant, with a further decline over time — to around just a 6% reduction as much as a year out, versus 61% with delta. A booster increased protection against infection with both variants, but protection was not as high against omicron.
Other analyses, including ones from Denmark and the Veterans Health Administration, have found similar results.
“The relative protection with omicron is less compared to prior variants (especially with just 2 doses rather than 3), but that protection still exists,” University of Pennsylvania infectious disease fellow Dr. Aaron Richterman told us in an email. “There is a lot of solid evidence supporting this.”
He is the lead author on a study, published on June 6 in Clinical Infectious Diseases, which found that among health care workers, third doses of the mRNA vaccines still protected against omicron infection, although much less so than against delta. Compared to unvaccinated employees, those triply vaccinated with the Pfizer/BioNTech vaccine were 54% less likely to become infected during the omicron period, versus 93% less likely during the delta era. Similarly, those triply vaccinated with the Moderna vaccine were 46% less likely to become infected during the omicron period, versus 96% less likely during the delta era.
The study did not identify a protective effect against infection with just two doses, but Richterman said he thought that was because of the small number of unvaccinated people in the study, which made the confidence interval very wide for those estimates.
“I would not take this to mean that two doses provide no protection, because when we look at the totality of evidence (including other studies with larger unvaccinated samples) there is some degree of measurable protection,” he said.
Notably, a Centers for Disease Control and Prevention study of the Pfizer/BioNTech vaccine in adolescents and kids, who became eligible for vaccination after adults, found that two doses of the vaccine reduced the risk of omicron infection by 31% among 5- to 11-year-olds and by 59% among teens 12 to 15 years old.
A study of basketball players and staff in the NBA during the omicron era also found that those who received a booster dose were 57% less likely to become infected with the coronavirus than those who were eligible but had not received a booster, indicating vaccination can prevent omicron infection to some degree.
Other data also show that the vaccines offer some protection, even if significantly reduced, against symptomatic infection with omicron. A study published in March in the New England Journal of Medicine, for example, found that in the U.K., two doses of the Pfizer/BioNTech vaccine were 65.5% effective at 2 to 4 weeks, falling to 8.8% after 25 or more weeks, with a Pfizer/BioNTech or Moderna booster increasing protection.
Richterman said it was “indisputable at this point” that vaccinated people are less likely to become infected than unvaccinated people. Other experts weren’t as definitive about that, but also thought it was likely to be true.
“I do think [vaccination] reduce[s] infection and there is some data out there to support this. I just don’t think we have enough data yet to be confident in this,” Matthew Fox, an epidemiologist at Boston University School of Public Health, told us in an email. “So, I’d like to see more before I’m sure.”
In any case, Fox said there’s no good evidence that vaccinated or boosted people would be at higher risk than the unvaccinated, as some have claimed.
“There is evidence in the sense that you can see some places where crude rates of infection in the unvaccinated are lower than in the vaccinated,” he said. But, he added, that “is unadjusted data, so you can’t rely on it.”
The vaccines, then, are likely still helping a person avoid infection with the omicron variant, even if only a little bit, and for a short period of time. (That limited protection is one reason why no one should rely solely on vaccination if they don’t want to get infected.) The primary purpose of vaccination, though, is to prevent serious illness — and on that front, the data are overwhelmingly clear that vaccination is still quite effective.
“The data generally suggest something like 20-30% efficacy against infection in the omicron era. Not high,” Johns Hopkins University epidemiologist Dr. David Dowdy said in an email. “But protection against severe disease remains strong.”
Indeed, numerous studies have found that there is a small decline relative to earlier variants, but the level of protection against the worst outcomes remains high. CDC analyses, for instance, show that two doses of an mRNA vaccine reduce the risk of hospitalization by 64% four to six months after the last dose, with protection rising to 84% with a booster after the same amount of time. Protection is even higher in the first months following a shot and against critical illness and death.
“We shouldn’t be expecting vaccination to provide long-lasting protection against infection,” Dowdy said, noting that protection against infection seems to last only a few months. “But the data are very clear that people who have been vaccinated and boosted are at much lower risk of hospitalization and death.”
Misconstruing Raw Data
The incorrect notion that vaccinated and boosted people are more susceptible to COVID-19 than the unvaccinated often comes from a misunderstanding of raw data, which cannot be used to reach conclusions about vaccine effectiveness.
The Walgreens data that our readers wondered about, for example, related to higher positivity rates in the vaccinated and boosted people who showed up to pharmacies to be tested for COVID-19, compared with those who were unvaccinated.
The Gateway Pundit shared a screenshot of a Walgreens “COVID-19 Index” dashboard with such figures and declared the numbers “shocking.” The site proceeded to inaccurately interpret the data as showing “the vaccines are not working as advertised.”
But as Walgreens had previously explained on its dashboard — and later said in a more detailed report — the positivity rates are unadjusted and can “lead to misinterpretation.”
In a May 11 update report, the company’s analysts, in partnership with scientists at Aegis Sciences Corporation, the firm performing Walgreens’ PCR tests, dug into the data to explore the differences between the vaccinated and unvaccinated groups that could affect the likelihood of someone testing positive for COVID-19 on either a PCR or rapid test (although the dashboard only showed results for PCR tests).
The analysis identified several differences that could explain the lower probability of unvaccinated people testing positive than the vaccinated groups, including being less likely to report having had close contact with someone with COVID-19, less likely to live in a county with a higher positivity rate, and more likely to report a previous COVID-19 infection. “These patients who survived were likely to benefit from natural immunity which provides some protection against future infections, further lowering the reported positivity rate in the unvaccinated group,” the report authors wrote.
Unvaccinated people were also more likely to be weekly repeat testers, who are more likely to test negative because individuals are not testing because of symptoms or an exposure.
And when the positivity rates were calculated just for those with a previous coronavirus infection, unvaccinated people were “significantly more likely” to test positive than vaccinated people, according to the report. “This supports previous findings regarding the ‘super immunity’ for patients who received the COVID-19 vaccination and had a previous COVID-19 infection,” the authors wrote. “While natural immunity does offer some protection for unvaccinated patients, previous infection and vaccination combined offers even more robust protection.”
Along similar lines, the analysis found that among older adults, a majority of whom reported testing for travel, “unvaccinated patients had significantly higher positivity compared to those vaccinated.”
A Walgreens spokesperson emphasized the limitations of the data on its dashboard, which is raw and unadjusted, unless otherwise noted. “This contributes to the overall picture of COVID-19 spread in a timely manner, but cannot be used to reach vaccine efficacy conclusions,” she said in an email. “As noted on the COVID-19 Index, in order to draw these important conclusions the data must be analyzed to control for factors including, age, repeat testing, recent or direct exposure to COVID-19 and pre-existing conditions among others.”
Certainly, the ability of the omicron variant to evade immunity is one reason why the Walgreens positivity data changed over time and why more vaccinated people are getting infected than before. But again, it doesn’t mean that vaccinated people are actually more susceptible to infection than if they hadn’t been vaccinated.
“Over time, more people are getting vaccinated, but also more people who are unvaccinated have gotten sick – which provides some level of protection going forward. It’s also true that immunity from the vaccine (or infection) against repeat infection does not last for a long period of time,” Dowdy said. “So, since not that many people have been vaccinated in the last ~3 months, vaccinated people are, in many cases, getting infected at similar levels to those who have not been vaccinated. But looking at hospitalizations and deaths, it’s clear that vaccines are still highly effective.”
Experts we spoke with cautioned against overinterpreting raw data that compares the vaccinated with the unvaccinated without attempting to control for other differences between the populations.
“It is really important to remember that you can’t just look at trends of covid and vaccination and draw conclusions about the effect of the vaccine. The reason for this is that those who are vaccinated are not the same as those who are not,” Fox said.
One huge difference is age. The older you are, the more likely you are to be vaccinated — and older people are much more likely to get sick and get severely sick, Fox said. Behavior and prior infection are also different.
What we really want to know, Fox said, is “among 20 year olds, or among 50 year olds or among 80 year olds (and really within those, among those with the same levels of exposure to the virus – something very hard to adjust for), are you more likely to be infected (and hospitalized, etc.) if you are vaccinated or unvaccinated. And all the high quality studies show that the vaccinated have lower rates, not higher.”
Avnika Amin, an infectious disease epidemiologist and postdoctoral research fellow at Emory University, also said it was problematic to jump to conclusions when the unvaccinated and vaccinated groups “aren’t totally comparable.” There are differences in who might seek out a test, which has become even more complicated more recently with the rise of rapid tests, she said, which generally aren’t reported to public health authorities.
“We have a harder time getting accurate rates now than we did earlier in the pandemic,” she said in an interview.
Those who are vaccinated and boosted are more likely to be more vulnerable to the coronavirus to begin with, she noted, and a previously infected person could be less likely to get vaccinated, since they are more protected against another infection than someone who has neither been infected or vaccinated before.
The CDC has been posting rates of COVID-19 cases and deaths among the unvaccinated, vaccinated and boosted on its dashboard. The data is adjusted for age, but not for other factors.
For the month of March, the dashboard shows that for people 12 years and older, the unvaccinated were 1.9 times more likely to test positive and 17 times more likely to die than those who were vaccinated and boosted.
Amin, who doesn’t represent the CDC, but was co-first author on a Morbidity and Mortality Weekly Report publication reporting similar data when the omicron variant first emerged in the U.S., acknowledged that this data was “imperfect,” but said that age is “a pretty big thing to adjust for.”
“It’s not just that your risk, if you’re exposed, your risk of getting sick increases with age, it’s also that you’re more likely to have an immunocompromised condition as you get older, you’re more likely to have other things that can put you at risk for severe COVID,” she said.
But, she said, there’s a reason why the dashboard is plastered with footnotes warning visitors about the potential problems with the data. And instead of reading too much into little blips in the data, she recommended using the information as a surveillance tool.
“The better way to think about this is the early signal of whether or not we need to be concerned about vaccine protection and whether it’s changing over time, or if it’s waning, or if maybe a new variant is coming up,” she said of the dashboard. Then, she said, scientists can conduct well-designed studies to investigate further.
Editor’s note: SciCheck’s COVID-19/Vaccination Project is made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. The goal of the project is to increase exposure to accurate information about COVID-19 and vaccines, while decreasing the impact of misinformation.
Sources
“Covid-19 Positivity by Vaccination Status Data Interpretation,” update of National Surveillance of COVID-19 Infections: Variants, Vaccination Status, and Viral Spread. Walgreens and Aegis Sciences Corporation. 11 May 2022.
“Comparing SARS-CoV-2 infection rate of vaccinated and unvaccinated populations doesn’t reflect the real COVID-19 vaccine effectiveness.” Health Feedback. 13 Apr 2022.
“Article by The Exposé failed to account for caveats listed in U.K. vaccine surveillance reports; falsely claims fully vaccinated people have weakened immunity.” Health Feedback. 5 Nov 2021.
Robertson, Lori. “Why It’s Easy to Misinterpret Numbers of Deaths Among the Vaccinated.” FactCheck.org. 1 Nov 2021.
“Omicron Variant: What You Need to Know.” CDC. Updated 29 Mar 2022.
Hubbard, Kaia. “CDC: Omicron Overtook Delta as Dominant Variant.” U.S. News & World Report. 28 Dec 2021.
Robertson, Lori. “Early Data on Omicron.” FactCheck.org. 22 Dec 2021.
Robertson, Lori and Jessica McDonald. “Q&A on the Omicron Variant.” FactCheck.org. 3 Dec 2021.
del Rio, Carlos and Preeti N. Malani. “COVID-19 in 2022—The Beginning of the End or the End of the Beginning?” JAMA. 27 May 2022.
International Vaccine Access Center (IVAC), Johns Hopkins Bloomberg School of Public Health. VIEW-hub. Accessed 10 Jun 2022.
Tseng, Hung Fu, et al. “Effectiveness of mRNA-1273 against SARS-CoV-2 Omicron and Delta variants.” Nature Medicine. 21 Feb 2022.
Hansen, Christian, et al. “Vaccine effectiveness against infection and COVID-19-associated hospitalisation with the Omicron (B.1.1.529) variant after vaccination with the BNT162b2 or mRNA-1273 vaccine: A nationwide Danish cohort study.” Research Square preprint. 30 Mar 2022.
Sharma, Aditya, et al. “Effectiveness of mRNA-based vaccines during the emergence of SARS-CoV-2 Omicron variant.” Clinical Infectious Diseases. 27 Apr 2022.
Richterman, Aaron. Clinical Fellow, Infectious Disease, Perelman School of Medicine. Emails to FactCheck.org. 6 and 7 Jun 2022.
Richterman, Aaron, et al. “Durability of SARS-CoV-2 mRNA Booster Vaccine Protection Against Omicron Among Health Care Workers with a Vaccine Mandate.” Clinical Infectious Diseases. 6 Jun 2022.
Fowlkes, Ashley L., et al. “Effectiveness of 2-Dose BNT162b2 (Pfizer BioNTech) mRNA Vaccine in Preventing SARS-CoV-2 Infection Among Children Aged 5–11 Years and Adolescents Aged 12–15 Years — PROTECT Cohort, July 2021–February 2022.” MMWR. 11 Mar 2022.
Tai, Caroline G., et al. “Association Between COVID-19 Booster Vaccination and Omicron Infection in a Highly Vaccinated Cohort of Players and Staff in the National Basketball Association.” JAMA. 2 Jun 2022.
Link-Gelles, Ruth. “COVID-19 Vaccine Effectiveness during Omicron.” ACIP meeting presentation slides. 20 Apr 2022.
Accorsi, Emma K., et al. “Association Between 3 Doses of mRNA COVID-19 Vaccine and Symptomatic Infection Caused by the SARS-CoV-2 Omicron and Delta Variants.” JAMA. 21 Jan 2022.
Andrews, Nick, et al. “Covid-19 Vaccine Effectiveness against the Omicron (B.1.1.529) Variant.” NEJM. 2 Mar 2022.
Fox, Matthew. Professor of Epidemiology, Boston University School of Public Health. Emails to FactCheck.org. 7 Jun 2022.
Dowdy, David. Associate Professor of Epidemiology, Johns Hopkins Bloomberg School of Public Health. Email to FactCheck.org. 6 Jun 2022.
“Weekly epidemiological update on COVID-19 – 8 June 2022.” WHO. 8 Jun 2022.Pajak, Rebekah. Walgreens spokesperson. Email to FactCheck.org. 8 Jun 2022.
Amin, Avnika. Postdoctoral Fellow, Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University. Phone interview with FactCheck.org. 6 Jun 2022.
“COVID Data Tracker.” CDC. Accessed 10 Jun 2022.
Johnson, Amelia G., et al. “COVID-19 Incidence and Death Rates Among Unvaccinated and Fully Vaccinated Adults with and Without Booster Doses During Periods of Delta and Omicron Variant Emergence — 25 U.S. Jurisdictions, April 4–December 25, 2021.” MMWR. 21 Jan 2021.
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