According to a pre-print retrospective cohort study posted on 19 December 2022 titled “Effectiveness of the Coronavirus Disease 2019 (COVID-19) Bivalent Vaccine” by Nabin K. Shrestha et al, more vaccinations correlate to more infections.
Recognizing that the so-called vaccine was less effective against the later variants, the researchers conducted this study to evaluate the effectiveness of the updated bivalent vaccine.
The study involved 51011 employees of the Cleveland Clinic Health System (CCHS) with a mean age of 42.3 years. The study period began on 12 September 2022 when the bivalent vaccine was made available to employees and finished on 12 December 2022.
Among these, 20689 (41%) had previously had a documented episode of COVID-19 and 12029 (24%) had previously had an Omicron variant infection. 44592 subjects (87%) had previously received at least one dose of vaccine, 42064 (83%) had received two doses, 27254 (53%) had received at least three doses, and 3858 (8%) had received four or more doses. 46340 (91%) had been previously exposed to SARS-CoV-2 by infection or vaccination.
It should also be noted that 10804 were bivalent-boosted by the end of the study, mostly using Pfizer (~89%), the remaining using Moderna.
The strength of this study is obviously its large sample size. However, it is limited to healthcare workers who may be more exposed to COVID-19 and just more crap in general, and we don’t know how this impacts vaccine effectiveness and one’s immune system. Also, approximately 75% are female. In any case, since this study is limited to such a group, it is perhaps still useful as a relative indicator.
As for the bivalent vaccine, the “calculated overall vaccine effectiveness from the model was 30% (95% C.I., 20% – 39%)”. Perhaps more intriguing is that figure 1 indicates that previous Omicron BA.4/BA.5 infection (and therefore its antibodies) is very effective against infection.
Not surprisingly, one was more likely to get infected if one hadn’t been infected with any variant previously. That being the case, figure 2 indicates that those with 0 doses had fewer infections than those who were vaccinated; the more doses, the worse.
Also not surprising is that the authors seem to be in denial about it (or pretending to be):
The association of increased risk of COVID-19 with higher numbers of prior vaccine doses in our study, was unexpected. A simplistic explanation might be that those who received more doses were more likely to be individuals at higher risk of COVID-19. A small proportion of individuals may have fit this description. However, the majority of subjects in this study were generally young individuals and all were eligible to have received at least 3 doses of vaccine by the study start date, and which they had every opportunity to do. Therefore, those who received fewer than 3 doses (>45% of individuals in the study) were not those ineligible to receive the vaccine, but those who chose not to follow the CDC’s recommendations on remaining updated with COVID-19 vaccination, and one could reasonably expect these individuals to have been more likely to have exhibited higher risktaking behavior. Despite this, their risk of acquiring COVID-19 was lower than those who received a larger number of prior vaccine doses. This is not the only study to find a possible association with more prior vaccine doses and higher risk of COVID-19. A large study found that those who had an Omicron variant infection after previously receiving three doses of vaccine had a higher risk of reinfection than those who had an Omicron variant infection after previously receiving two doses of vaccine. Another study found that receipt of two or three doses of a mRNA vaccine following prior COVID-19 was associated with a higher risk of reinfection than receipt of a single dose.
Granted, these results don’t reveal the cause of the increased risk associated with a higher number of vaccine doses and one is supposed to speculate in the discussion… but really?
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