The protection against Covid-19 is generally, but especially in men, the elderly, and frail individuals, limited in duration, as a recent study from Sweden shows:
Clinical trials have demonstrated the high efficacy of the Coronavirus Disease 2019 (Covid-19) vaccines against the risk of infection and severe illness. However, reports of breakthrough infections and waning immunity have raised concerns about the duration of vaccine protection and the necessity of additional booster shots. Currently, there is some evidence that the vaccine's effectiveness against infection diminishes for up to six months after vaccination, while protection against severe illness appears to be better maintained. However, the evidence is limited and inconsistent, partly due to the evaluation of vaccines, which may have different long-term effects. In particular, it is not known whether the vaccine's effectiveness persists beyond six months.
The new facts: In this extensive Swedish study, the efficacy of the BNT162b2 vaccine (BioNTech/Pfizer) against symptomatic infections gradually decreased from 92% in the first month to 47% in months 4-6. No efficacy was observed from month 7 onward. The efficacy of mRNA-1273 (Moderna) declined somewhat more slowly, while the efficacy of ChAdOx1 nCoV-19 (AstraZeneca) was generally lower. Overall, efficacy declined more rapidly in men and older individuals. For the parameters of hospitalization or death, efficacy (of each vaccine) decreased from 89% in the first month to 42% from month 6 onward in the overall population. A more pronounced decline was observed particularly in men, elderly frail individuals, and those with comorbidities. With AstraZeneca , protection against coronavirus infection was no longer present after four months. The BioNTech/Pfizer offered only 23% protection after six months. The Moderna Johnson & Johnson vaccine was not used in Sweden, therefore no data is available for this vaccine.
Conclusions from the available data: The efficacy of vaccines against symptomatic COVID-19 infections progressively declines over time for all subgroups, but to varying degrees and more rapidly in males, older individuals, and frail individuals, depending on the type of vaccine. Efficacy against hospitalizations or death appears to remain high for up to 9 months, except in men, older individuals, and those with underlying health conditions. This reinforces the evidence-based need for a third booster dose.
Prof. Dr. Hartmut Göbel: "The data suggests that we should have started full-scale booster vaccinations no later than August 2021 to effectively prevent the current fourth wave. As it stands, things will get bad. It's four months past the eleventh hour."
The figure shows the duration of action of the different vaccines.
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