THL analysis: elderly members of risk groups clearly benefit most from fourth coronavirus vaccine doses
Members of high-risk groups aged 80 years and over benefit most from being vaccinated against coronavirus for a fourth time, according to a working paper issued by THL.
THL analysed the effectiveness of fourth coronavirus vaccine doses on members of risk groups over the age of 60 and others in the same age range in three different epidemic situations.
The analysis delved into the effectiveness of vaccinating against coronavirus using the NNV number - the Number Needed to Vaccinate. NNV is an estimate of how many people would need to be vaccinated for a fourth time to prevent one case of coronavirus infection requiring special care within 30 days of the fourth vaccination.
The NNV was calculated by evaluating the risk of having to resort to specialised health care in April and May 2022 among those vaccinated against coronavirus for a third time over four months ago. The analysis was based on an estimate that a fourth dose reduces the risk of coronavirus requiring specialised health care by 50 percent compared with someone who was vaccinated for a third time four months earlier.
The smaller the NNV is, the greater the effectiveness of the vaccine. In a scenario in which the number of coronavirus infections dropped to half of those recorded in April-May 2022, the NNV figures in the different group were as follows:
- about 1,800 for those aged 80 or more who are part of a risk group
- about 6,300 for those aged 80 who are not part of a risk group
- about 4,400 for those aged 70-79 who are part of a risk group
- about 12,500 for those aged 70-79 who are not part of a risk group
- about 12,600 for those aged 60-69 who are part of a risk group
- about 17,200 for those aged 60-69 who are not part of a risk group
“The NNV doubles when the number of infections in society is halved. The effectiveness of vaccinations therefore drops significantly as the number of infections decreases”, says Eero Poukka, Medical Specialist at THL.
“Conversely, this means that if the number of infections starts growing fast, it might be justified to give fourth vaccine doses to younger age groups”, Poukka adds.
THL is now recommending that those in age groups that are vulnerable to the risk of severe coronavirus disease – those aged 80 years and over, and those aged 70–79 who belong to a risk group – should get a fourth vaccination. Additionally, the fourth coronavirus vaccine dose is recommended for those living in elderly care homes and older people under organised home care or informal care as well as other older people whose health and functional capacity have deteriorated correspondingly and who cannot cope alone at home. THL recommends a fifth dose of the coronavirus vaccine for those with severe immune deficiencies.
THL plans to recommend the extension of fourth doses of coronavirus vaccines in the late summer. A final recommendation will be ready at the beginning of August at the latest.
Protection given by the vaccine against a severe form of the disease weakens gradually
According to the updated coronavirus vaccine strategy of the Ministry of Social Affairs and Health, the goal of coronavirus vaccines is to reduce the risk of severe disease and to prevent deaths.
Coronavirus vaccines provide protection against both coronavirus infections and the severe form of the disease, but the protection against infection weakens much faster than than protection against a severe form of the disease. With the omicron variant, the protective effect against an infection is moderate and short-term at best, but against a severe form of the disease, it is good at the very least, and lasts for several months.
Factors affecting the risk of an individual contracting a severe form of coronavirus disease, include age and underlying diseases, immunity protection against a severe case of coronavirus disease, as well as the current and future epidemic situation.
When making recommendations for coronavirus vaccines, factors that are considered include what kind of protection that a vaccination will bring an individual against severe coronavirus disease, as well as the costs of vaccination. The analysis of the effects of coronavirus vaccinations must be analytical and knowledge-based, in order to gain the greatest benefit, both medically, and in terms of health economics.
“Reducing severe forms of the disease is important both from a human, and a societal point of view. Effective use of vaccines protects the most vulnerable, avoids placing excess burden on the health care system, and frees up nurses to handle other matters”, says THL Chief Physician Hanna Nohynek.
“Healthy persons under the age of 60 continue to be well protected against severe coronavirus disease, even if the protective effect of the vaccines might decline slightly”, Nohynek observes.
On 11 July 2022 the European Centre for Disease Prevention and Control ECDC and the European Medicines Agency EMA urged member states to consider administering fourth coronavirus vaccinations to all those aged 60 and above and to members of risk groups, noting that national authorities are making their own recommendations and that authorities making final decisions on the use of coronavirus vaccines consider the epidemiological situations of their countries.
“We are still looking into the background information of the ECDC and EMA guidelines. The coronavirus situation in Finland is currently relatively calm and we monitor the figures daily. Recommendations can be changed quickly, if necessary”, Nohynek says.
Multiple vaccinations are a new situation
There is a completely new situation with coronavirus vaccinations: no previous vaccination campaigns have been conducted in which a vaccine is given repeatedly at intervals of 4–6 months. There is a concern that repeated vaccinations might weaken the immune protection against coronavirus in the long term if the same vaccine is used.
Repeated vaccinations also pose other challenges. Finland has about 1.6 million people over the age of 60. Offering them numerous doses of vaccines at intervals of 4–6 months would require a significant increase in trained health care personnel. This would be essential to prevent other tasks of health care from being neglected, and to keep the treatment of other diseases from suffering. This also needs to be considered when drafting vaccination programmes at the population level, and a model needs to be sought which produces the greatest overall health benefit in proportion to the input.
The analysis in the discussion paper was produced in the early summer of 2022 as the expansion of fourth vaccinations was evaluated. The work has been extended to younger age groups and an advance recommendation to expand the use of vaccinations in August-September was based on it.
