nett wrote: ↑Wed Aug 25, 2021 9:54 pm
Brand new study out of Israel basically confirms what some of us already knew.
Vaccinated folks are 13x more likely to be infected, and 27 times more likely to be symptomatic than those with natural immunity, espectively.
https://www.medrxiv.org/content/10.1101 ... 1.full.pdf
Model 1 – previously infected vs. vaccinated individuals, with matching for time of
first event
In model 1, we matched 16,215 persons in each group. Overall, demographic
characteristics were similar between the groups, with some differences in their
comorbidity profile (Table 1a).
During the follow-up period, 257 cases of SARS-CoV-2 infection were recorded, of
which 238 occurred in the vaccinated group (breakthrough infections) and 19 in the
previously infected group (reinfections). After adjusting for comorbidities, we found a
statistically significant 13.06-fold (95% CI, 8.08 to 21.11) increased risk for
breakthrough infection as opposed to reinfection (P<0.001). Apart from age ≥60
years, there was no statistical evidence that any of the assessed comorbidities
significantly affected the risk of an infection during the follow-up period (Table 2a).
Obvious difference in vaccinated versus unvaccinated when matched by date which is skewing the data badly in the USA.
Model 3 - previously infected vs. vaccinated and previously infected individuals
In model 3, we matched 14,029 persons. Baseline characteristics of the groups are
presented in Table 1b. Examining previously infected individuals to those who were
both previously infected and received a single dose of the vaccine, we found that the
latter group had a significant 0.53-fold (95% CI, 0.3 to 0.92) (Table 4a) decreased risk
for reinfection, as 20 had a positive RT-PCR test, compared to 37 in the previously
infected and unvaccinated group. Symptomatic disease was present in 16 single dose
vaccinees and in 23 of their unvaccinated counterparts. One COVID-19-related
hospitalization occurred in the unvaccinated previously infected group. No COVID19-related mortality was recorded
Shows a gain from vaccination, but not time matched. Benefit seems small but the study was also limited by number of infections
Although the results could suggest waning natural
immunity against the Delta variant, those vaccinated are still at a 5.96-fold increased
risk for breakthrough infection and at a 7.13-fold increased risk for symptomatic
disease compared to those previously infected. SARS-CoV-2-naïve vaccinees were
also at a greater risk for COVID-19-related-hospitalization compared to those who
were previously infected.
Our study has several limitations. First, as the Delta variant was the dominant strain in
Israel during the outcome period, the decreased long-term protection of the vaccine
compared to that afforded by previous infection cannot be ascertained against other
strains. Second, our analysis addressed protection afforded solely by the
BioNTech/Pfizer mRNA BNT162b2 vaccine, and therefore does not address other
vaccines or long-term protection following a third dose, of which the deployment is
underway in Israel. Additionally, as this is an observational real-world study, where
PCR screening was not performed by protocol, we might be underestimating
asymptomatic infections, as these individuals often do not get tested.
This analysis demonstrated that natural immunity affords longer lasting and stronger
protection against infection, symptomatic disease and hospitalization due to the Delta
variant of SARS-CoV-2, compared to the BNT162b2 two-dose vaccine-induced
immunity. Notably, individuals who were previously infected with SARS-CoV-2 and
given a single dose of the BNT162b2 vaccine gained additional protection against the
Delta variant. The long-term protection provided by a third dose, recently
administered in Israel, is still unknown.
