Tegnell: That's why the numbers on antibodies are so low
According to the Public Health Authority's mathematical model, 17 percent of the population in Stockholm would have been infected by the corona virus on April 11. However, according to the authority's recently presented antibody study, only 7.3 percent of Stockholmers had been infected around that period.
- There are more explanations for not digging into the figure, says state epidemiologist Anders Tegnell.
On April 21, the Public Health Authority published the results of a mathematical model used to measure the spread of covid-19 in Stockholm County. According to the report, about 26 percent of Stockholmers were infected with covid-19 around May 1, and 17 percent would have been infected on April 11.
Therefore, when the authority presented the results of the first antibody study earlier this week, many were surprised by the relatively low proportion of Stockholmers who had developed antibodies at week 18 - only 7.3 percent.
Because it takes a few weeks before the body's immune system develops antibodies, the figures reflect the state of infection from earlier in April - around week 15 (April 6-12), state epidemiologist Anders Tegnell estimated.
Flock immunity may be delayed
The public health authority's results are not the first to show low levels of antibodies. A study in Spain showed that only five percent of the population had antibodies - despite many becoming infected with the virus.
The results have subsequently been included in the discussion on immunity in Sweden.
In an interview with Lifescience, infection professor Björn Olsen says it may take a long time before Sweden reaches herd immunity:
- I think it will take several years before we have herd immunity. But this will go away anyway, partly because of the social distance. In Sweden, however, it may take longer as we are in a plateau phase that has been going on for a very long time.
However, both Anders Tegnell and other representatives from the authorities have emphasized that Sweden's strategy is not to obtain flock immunity.
"An immunity that completely stops the infection, there is no reason to believe it will happen," Tegnell said at Wednesday's press conference.
Not entirely clear
However, the question remains as to why the Public Health Agency's forecast on antibodies differed so much from the results of the study.
According to Tegnell, there may be several explanations. On the one hand, it is not entirely clear how long it will take to develop antibodies, and on the other hand, it is not clear if everyone who is infected actually develops antibodies, he says.
- In addition, it must be taken into account that these are samples from health centers, during a period when probably quite a few people avoid going to the health center.
In other words, there may be problems with the representativeness of the sample in the antibody study, says Anders Tegnell.
- It is probably the most seriously ill people who come to the health center. These blood tests, which are normally considered quite representative, are probably not the same today.
Complete the selection
TT: Will you still measure antibodies by the same method?
- That's what we're discussing now. It certainly needs to be supplemented in some way, says Anders Tegnell.
In reality, the proportion of infected people in Stockholm at the beginning of April was probably somewhere between the prognosis and the antibody study, he says.
- Exactly where we do not know, and where we are closest we do not know. There are measurements from Karolinska that have shown on higher numbers, and measurements that we have received from any company that shows significantly higher numbers, so one should be very careful to draw too large conclusions from individual values and individual studies. It's not our role to get caught up in it.
