A new Swedish study has found that COVID-19 vaccines show diminishing effectiveness against infection – with “no effectiveness” after 211 days for the Pfizer vaccine, while the Astra Zeneca vaccine shows “no effectiveness” from day 121 onwards. The research was published as a preprint on the Lancet.
“The effectiveness against severe illness seems to remain high through 9 months, although not for men, older frail individuals, and individuals with comorbidities,” the research found.
The Covid vaccines “do not give lasting protection to older people or those with an underlying health condition,” the study said.
The results “suggested a notable waning vaccine effectiveness against severe disease among older frailer individuals and individuals with any comorbidity (underlying health conditions) from 6 months through 9 months after vaccination.”
“Vaccine effectiveness against symptomatic Covid-19 infection wanes progressively over time across all subgroups, but at different rate according to type of vaccine, and faster for men and older frail individuals. The effectiveness against severe illness seems to remain high through 9 months, although not for men, older frail individuals, and individuals with comorbidities. This strengthens the evidence-based rationale for administration of a third booster dose,” researchers concluded.
The researchers acknowledge that no previous study has had a follow-up time as long as 9 months to support their results, but note that their findings extend those from the UK, showing decreasing effectiveness against hospitalisation among older adults in a clinically extremely vulnerable group after 5 months.
“Vaccine effectiveness of BNT162b2 [Pfizer] against infection waned progressively from 92% .. at day 15-30 to 47% .. at day 121-180, and from day 211 and onwards no effectiveness could be detected ,” the study found.
For Moderna, effectiveness “waned slightly slower” and was estimated to 59% from day 181 and onwards.
In contrast, effectiveness of Astra Zeneca “was generally lower and waned faster, with no effectiveness detected from day 121 and onwards,” the study found
Researchers explain that a reasonable explanation for this can be found in the fact the vaccine induces a lower induction of memory T- and B- cells in older adults, and that production of plasma cells that could produce lower levels of antibody for decades is impaired. The study also discovered that vaccine effectiveness waned quicker in men than in women.
They also wrote: “In support, in the present study the overall most important risk factor for lower vaccine effectiveness was higher age, both for symptomatic infection and severe disease. Other risk factors included individuals with homemaker service and underlying common medical conditions, such as diabetes and hypertension, as well as male sex, where similar waning effectiveness against severe disease was noted.
“For example, from 6 months through 9 months after vaccination, the effectiveness against severe disease was a borderline significant 52% in men compared to a robust 73% in women. Although there has been no previous study reporting waning vaccine effectiveness according to sex, these findings are supported by studies showing a lower vaccine-elicited immune response along with a more rapid decline in neutralizing antibody titers in men compared to in women.”
The study, published as a preprints while awaiting peer review, investigates the effectiveness of COVID-19 vaccination against the risk of symptomatic infection, hospitalisation, and death up to 9-months post-vaccination for the total population of Sweden.
Whilst initial clinical trials showed a high efficacy of the Pfizer-BioNTech, Modera and Oxford/AstraZeneca COVID-19 vaccines, reports on breakthrough infections and decreasing immunity have created concerns regarding the duration of protection.
The authors state that, from the data currently available, “Collectively, there is insufficient evidence to determine vaccine effectiveness beyond 6 months.” They explain that differing results in recent studies carried out in the US, the UK and Qatar may be linked to several factors, including the evaluations of vaccines that may have different long-lasting side effects, a low proportion of old participants, and varying and relatively short follow-up times.
In other news, a NPHET model has suggested that COVID immunity after being infected could be “permanent,” rather than lasting a maximum of 9 months, as previously suggested.
As reported by Gript, “A recent preprint in the scientific journal Cell found that a longitudinal analysis showed “durable and broad immune memory” after an infection with Covid-19 “with persisting antibody responses and memory B and T cells”. Moreover, they took aim at the “notion” that immunity conferred after recovery from Covid-19 might be short-lived, saying that the investigation showed the generation of long-lived plasma cells and “refute the current notion that these antibody responses to human coronaviruses are short lived.”
“A review of studies of immunity after infection published in the Lancet this month found that reinfection with Covid-19 after recovery from previous infection was very low – with studies suggesting it at between 0 and 1%. After data from Israel, then one of the most vaccinated countries in the world was examined, Science reported in August that “never-infected” people who were vaccinated were “six to 13 times more likely to get infected than unvaccinated people who were previously infected with the coronavirus.”