IMMUNITY FROM COVID-19 VACCINES DECREASES OVER TIME REGARDLESS OF AGE
02.11.2021
Immunity From COVID-19 Vaccines Decreases Over Time Regardless of Age
Israeli researchers have showed that the immunity against the Delta variant, received from the Pfizer vaccine against COVID-19, decreases for all age groups in the months following vaccination.
As reported by Technion - Israel Institute of Technology in Haifa, COVID-19 infection rates were higher in adults of ages 60 and up having received their final vaccination doses in January than those having received their final doses in July.
Similarly, the rates of infection were higher in adults of ages 40 to 59 receiving their final doses in February, and in individuals of ages 16 to 39 doing so in March, compared to the same groups receiving the final dose in, respectively, April, and May.
With these numbers in mind, one thing to consider is that the individuals deemed fit to receive vaccines earlier involved health care workers, and individuals of 16 to 59 years of age with suppressed immunities. Since the vaccination duration results of these groups were derived from selected samples and may be controversial, these results should be interpreted with caution.
Decreasing levels of immunity and the Delta variant itself have caused the need for additional doses. Previous studies in the US showed that the increase in infections was due to decreased immunity levels, rather than the Delta variant.
Israeli researchers reported that 98% of the infections in June were due to the Delta variant; and therefore, they were monitoring the data from July 1 to 31 on everyone vaccinated before June 1. Individuals past Day 7 of their second vaccination were deemed “Fully Vaccinated”.
The study states that PCR test results were positive for 13 426 of 4.8 million fully-vaccinated residents; with 403 residents developing serious cases of COVID-19. The confirmed general rate of infections among adults of ages 60 and up were 3.3 per mille for those vaccinated in the second half of January; while the number was 2.2 per mille for those vaccinated in the second half of February.
While the rates of severe cases in individuals of ages 60 and up were higher in those vaccinated in January compared to those vaccinated in March; the rates in individuals of ages 40 to 59 were much higher in those fully vaccinated in February, than in April (with a wide confidence interval for the data analyzed). Authors state that the number of severe cases in individuals between ages 16 and 39 are too low for a conclusion.
A similar situation regarding the prevalance of severe cases was the case in older individuals. 0.34 per mille of the COVID cases in individuals of ages 60 and up vaccinated in January were severe, compared to 0.12 per mille for individuals fully vaccinated in the April-May period.
In their study, researchers also stress the factors that may potentially affect the analyses such as pre-existing diseases, unmeasurable factors to confuse analysts, and sources of prejudice.
The results of this study constituted the epidemiological background for the Israeli Ministry of Health resolution greenlighting a third dose for individuals past at least their 5th month of vaccination as of July 30, 2021.
Currently, the CDC (The Center for Disease Control and Prevention, USA) recommends additional doses of COVID-19 vaccines past at least Month 6 of the first two-dose series for individuals over the age of 65, as well as those over 18 in long-term care facilities with high medical risks, and those exposed to COVID-19 professionally, or institutionally.