Here’s the story that led me to the study. The story would have one believe that:
COVID-19 vaccination confers much greater protection against individuals being hospitalized or rushed to emergency departments for any cause—not just COVID-19 infection—compared to individuals who’ve been previously infected by the disease but not vaccinated against it, according to a new study.
Researchers with the Regenstrief Institute, the Indiana University School of Medicine and the Vanderbilt University Medical Center found that all-cause death and hospital admission rates for vaccinated individuals are 37% lower than for those who’ve been previously infected by COVID-19 but had not been vaccinated. In addition, the rates of ED admissions for vaccinated individuals for all causes is 24% lower for the vaccinated than the unvaccinated, according to the study published in the American Journal of Public Health.
These are some stark claims! But the story continues:
Perhaps counterintuitively, the study also finds that vaccinated individuals are more likely to become infected by COVID-19 than unvaccinated individuals. Incidence of COVID-19 infection is 6.7% for the vaccinated as compared to 2.9% of those who’d not gotten vaccinated but had prior infections, although vaccination better protected against severe SARS-CoV-2 infection than prior infection, according to the study.
Did you spot the trickery? I hate pointing out the obvious but did you notice that in the first point, the part you’re supposed to latch onto, the writer of the story used big numbers like 37% and 24%, and in the second point, the one that is supposed to not stick in your brain as important, they used small, absolute numbers like 6.7% and 2.9% (that’s around 57% btw)?
Enough with the story. Feel free to read it at your leisure. Let’s get onto the study. Bear with me, as I’m not a scientist, nor very good at math.
The results (red labels are mine, everything else is as presented):
From the INPC, we identified 2 798 709 unique vaccine recipients and 736 193 individuals with documented SARS-CoV-2 infection between November 29, 2020, and February 9, 2022. From these, we matched 267 847 vaccine recipients with the same number of infected participants (Figure 1). The demographic and clinical characteristics of the 2 groups of participants are presented in Table 1.
So half a million people participated in the study (267,847 vaccine recipients paired with the same number of previously infected participants).
Immunity wanes over time (emphasis mine)
The study concludes:
Strong and consistent evidence shows that mRNA vaccines BNT162b2 and mRNA-1273 and the Janssen vaccine JNJ-78436735 confer considerable protection to fully vaccinated individuals against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, severe illnesses requiring hospitalization, and mortality.1–6 However, vaccine effectiveness is not 100%, and the risk of breakthrough infections remains, especially with newer variants.7,8 Furthermore, data and opinions diverge on the extent of the waning immunity provided by the mRNA vaccines.9,10 While a population-based observational study suggested that immunity waned in individuals within 2 months after completing the 2-dose sequence of the BNT162b2 vaccine,11 a randomized clinical trial showed that 6 months after vaccination, the BNT162b2 vaccine’s effectiveness against SARS-CoV-2 infection remained strong at higher than 86%; its effectiveness against the severe disease was 96.7%.12
These impressive numbers are picked from a study done in Nov, 2021.
Natural immunity induced by SARS-CoV-2 infection also protects against reinfection. Systematic reviews of immunological evidence suggested that SARS-CoV-2‒specific immunity appeared soon after infection.13,14 Extensive observational studies confirmed the significantly reduced risk for subsequent infection by more than 80% for at least 6 to 12 months in individuals with previous infection.15–17 Data are mixed on the relative levels of protection conferred by vaccination versus infection.18–20 Less understood is the real-world time course of the protective effects of previous infection and vaccination against new infection acquisition and all-cause mortality and hospitalization in persons of different age groups. Unlike COVID-19‒specific outcomes used by earlier studies, all-cause emergency department (ED) visits, hospitalizations, and mortality cover a broader spectrum of health consequences of the disease.
Incidence of infection, reinfection
Cumulative incidence rates of events of interest were estimated and are presented graphically in Figure 2. Panel A shows a significantly higher cumulative incidence of infection or reinfection in vaccine recipients than those with previous infection (P < .001). Six months after the index date, the cumulative infection rate in the vaccinated was 6.7% (95% confidence interval [CI] = 6.6%, 6.9%), more than twice the rate in those with previous infections at 2.9% (95% CI = 2.9%, 3.0%).
“More than twice the rate” means greater than 50%. That’s that 57% number I came up with earlier. But also note that the raw values are 6.7% and 2.9%. Those are biggish numbers so should carry more weight statistically.
All-cause ED Visits
Figure B (available as a supplement to the online version of this article at https://ajph.org) shows that the cumulative incidence of all-cause ED visits was significantly lower in vaccinated individuals (P < .001). At 6 months, 6.6% (95% CI = 6.5%, 6.7%) of the individuals with previous infection and 5.0% (95% CI = 4.9%, 5.1%) of the vaccinated individuals had recorded ED visits.
Vaccinated folks scored better here. Only 5.0% visited the emergency department while 6.7% unvaccinated but previously infected visited the emergency department. That’s a difference of only 1.7%, yet can also be represented by a percentage change. This is how the study can claim unvaccinated but previously infected people are 24% more likely to visit the ED.
All-cause hospitalization
Figure C (available as a supplement to the online version of this article at https://ajph.org) shows that the all-cause hospitalization rate was also significantly lower in the vaccinated (P < .001). Six months after the index date, 1.9% (95% CI = 1.8%, 1.9%) of the previously infected individuals and 1.2% (95% CI = 1.1%, 1.3%) of the vaccinated had recorded hospitalization.
Another huge win for the vaccinated! Only 1.2% of those virtuous souls had a hospital stay for any reason, while a whopping 1.9% of the unvaccinated but previously infected fools spent the night at the hospital. That is a 0.7% gain for team covax. It’s not much, but definitely worth talking about. Especially so if you convert it to the scarier looking 37%.
Mortality Rate
This is the big one. The really big one. There’s just so much here. did I mention that it’s the big one yet?
Figure D (available as a supplement to the online version of this article at https://ajph.org) shows that the mortality rate was also significantly lower in the vaccinated (P < .001). Six months after the index date, mortality rates were respectively 0.51% (95% CI = 0.48%, 0.54%) in the previously infected and 0.32% (95% CI = 0.29%, 0.34%) in the vaccinated.
This is (as far as I can tell) overall mortality. The study breaks these number down further by age group later. Did you see the big admissions? All of them? It’s like one of those picture comparison games in kid’s magazines. I’ll point out the obvious ones.
Vaccinated individuals gained… wait for it… an astounding 0.19% REDUCTION IN RISK OF DEATH from a covid-19 infection. Or as the study and story claim, they’re 37% less likely to die. I’m not even going to look at the bits where the vaccinated have a 0.32% chance of dying from their first covid infection, and certainly not going to consider that they’re 57% more likely to have one. And we should probably completely ignore that bit about the unvaccinated morons who somehow survived their first infection, just to face a 0.51% chance that THEY’RE GOING TO DIE come the second infection.
The study goes on to do something called age stratification. If you want to take my word for it, the gist is that in younger groups, the numbers aren’t much different in terms of infection rate. The study then goes through the various age groups essentially painting the picture we’ve already seen about immunity. Younger kids get infected more often but are quite resilient. Young to middle-aged folks have built a pretty broad immunity to things in general, and in the elderly, the immune system starts to wane. We knew this all the way back in 2020.
The big takeways for me are the studies claimed mortality rates (less than 1%… again something we knew in 2020), the insignificant difference in mortality rate gain in the vaccinated, and the admission that vaccinated individuals are more than 50% likely to be reinfected with sars-cov-2. This latter implies that if they’re more likely to be reinfected, they must be more likely to spawn mutations and retransmit.