THL recommends shorter interval for third coronavirus vaccine – third doses for at-risk groups can be offered with 3–4 week interval

The Finnish Institute for Health and Welfare (THL) recommends a shorter interval for a third coronavirus vaccination. According to the recommendation, those aged 60 and above, as well as other previously defined at-risk groups may be given a third vaccination when 3–4 months have passed from their second dose. For those under the age of 60 who are not part of an at-risk group, the third vaccine dose may be offered 4–6 months after the second dose. The earlier recommendation for a vaccine interval was 5–6 months for all the above groups.

The new recommendation came after new information about the Omicron variant.

“Omicron has spread very quickly and efficiently around the world. Preliminary studies indicate that two vaccine doses do not give as good protection against mild cases of the disease as they did with the previous coronavirus variants”, says THL Head Physician Hanna Nohynek. 

With third vaccine doses it is important to move forward quickly according to the national COVID-19 vaccination strategy and the vaccination order set by Government decree, moving from the oldest age group to the younger ones. Regional flexibility in moving forward with vaccinations in this order is important. Municipalities organise the vaccinations and report regionally on their vaccination schedules. 

“Administering the third COVID-19 vaccine doses to those 60 years old and above and to other at-risk groups must be a priority. Booster vaccinations for those who are not part of an at-risk group must not cause a delay in giving third doses for the elderly or for others at risk of a severe case of the disease, because in younger age groups the risk that those who have been vaccinated would get a serious case of coronavirus disease is low. Municipalities must also be guaranteed adequate resources to enable giving third doses on a fast schedule”, says THL Chief Specialist Mia Kontio.

The THL recommendation is based on a statement issued at a meeting of the National Advisory Committee on Vaccines (KRAR) on 16 Dec. 2021 and is in line with guidelines from the European Centre for Disease Prevention and Control (ECDC) and the European Medicines Agency (EMA).

Goal: securing resource capacity of hospital care

A fairly small portion of the Finnish population, estimated at less than one in ten, have been infected by the coronavirus. In addition, more than half a million people in Finland over the age of 12 are still fully unvaccinated.

Further information is needed on the degree of protection that the Finnish population has against the Omicron variant and the seriousness of the clinical pictures that the variant presents. According to preliminary information from different countries, Omicron can cause a mild form of the disease among those who have been vaccinated twice. However, two vaccine doses do not provide sufficient protection against the spread of the virus from one person to another.

“The situation enables the rapid spread of the virus. Even if serious forms of the disease requiring hospital care were to develop only to a small portion of those who are infected, a powerful wave of the epidemic could endanger the resource capacity of health care”, Nohynek says.

Difficult clinical pictures can best be prevented by improving coverage of the first and second vaccine doses and by giving boosters to at-risk groups quickly and comprehensively. Preventing a single case of coronavirus disease requiring hospitalisation requires administering third doses to ten times as many elderly people compared with the number of recipients of the basic course of two doses. The numbers are considerably higher, the younger the people involved are.

“To manage the epidemic, it would be very important to boost vaccination coverage for the first and second doses. Vaccine doses are arriving in Finland at the end of the year and early next year at an even pace, so there will be enough for all vaccinations, including the first and second doses”, Kontion says.

Boosters protect against Omicron

A British study has evaluated the effectiveness of COVID-19 vaccines that are also used against the Omicron variant in Finland. Vaccine protection against Omicron appeared to be lower than against the Delta variant, according to a study conducted jointly by the UK Health Security Agency, Imperial College, and Oxford University. 

“More than six months after the second dose of the coronavirus vaccine, protection against a mild illness caused by Omicron had fallen to 34 percent, while against Delta it remained at 64 percent”, Nohynek says.

According to the study, protection after the third dose had risen to 76 percent against a mild disease caused by the Omicron variant. Protection given by a third vaccine against infection caused by the Delta variant was as high as 93 percent. 

“The Omicron variant is capable of dodging protection based on antibodies. This protection can be at least temporarily improved by third vaccine doses, which increase the antibody level”, says Merit Melin, Research Manager at THL. 

According to researched knowledge collected so far, cell-mediated immunity, with protection against a severe disease, appears to hold, also among those with two vaccinations

Further information:

Hanna Nohynek
head physician
THL
[email protected] 

Mia Kontio
Chief Specialist
THL
[email protected] 

Merit Melin
Research Manager
THL
[email protected]