Vaccination protection against Covid-19 is generally limited in time, but particularly in men, the elderly and the frail, as a recent study from Sweden shows: Clinical trials have shown
high effectiveness of the coronavirus disease 2019 (Covid-19) vaccines against the risk of Infections and serious illnesses have been documented. However, reports of breakthrough infections and waning immunity have raised concerns about the duration of vaccine protection and whether additional booster doses are warranted. There is currently some evidence that the effectiveness of the vaccine against infections wanes up to 6 months after vaccination, although protection against severe disease appears to be better maintained. However, the evidence is limited and inconsistent, in part due to the evaluation of vaccines, which may have different long-term effects. In particular, it is not known whether the effectiveness of the vaccine lasts beyond 6 months.

The new facts: In this large Swedish study, the effectiveness of the BNT162b2 (Biontech/Pfizer) against symptomatic infections gradually decreased from 92% in the first month to 47% in months 4-6. Effectiveness was no longer observed from the 7th month onwards. The effectiveness of mRNA-1273 (Moderna) declined somewhat more slowly, while the effectiveness of ChAdOx1 nCoV-19 (AstraZeneca) was generally lower. Overall, effectiveness decreased more quickly in men and older people. For the parameters of hospitalization or death, the effectiveness (of each vaccine) decreased from 89% in the first month to 42% from the 6th month in the overall population. A more pronounced decline was particularly evident among men, older frail individuals and those with comorbidities. At Astrazeneca, there was no longer any protective effect against coronavirus infection after just four months. Biontech/Pfizer vaccine only protected 23 percent after six months. The active ingredient from Moderna showed the comparatively highest protective effect of around 60 percent after six months. The active ingredient from Johnson & Johnson has not been used to vaccinate in Sweden, so no data is available for this vaccine.

Conclusions from the available data: The effectiveness of the vaccines against symptomatic Covid-19 infections decreases progressively over time for all subgroups, but to different degrees depending on the type of vaccine and more rapidly in males, the elderly and the frail. Efficacy against hospitalization or death appears to remain high up to 9 months, although not in men, the elderly and people with comorbidities. This strengthens the evidence-based need for administering a third booster dose.

Prof. Dr. Hartmut Göbel: “The data suggests that we should have started booster vaccinations at full speed by August 2021 at the latest in order to effectively prevent the current fourth wave. This is how things will get bad. It’s 4 months past 12.”

The figure shows the duration of action of the different vaccines.

 
Source: Nordström, Peter and Ballin, Marcel and Nordström, Anna, Effectiveness of Covid-19 Vaccination Against Risk of Symptomatic Infection, Hospitalization, and Death Up to 9 Months: A Swedish Total-Population Cohort Study. Available at SSRN: https://ssrn.com/abstract=3949410 or http://dx.doi.org/10.2139/ssrn.3949410