FHM's antibody tests deviate from the forecasts - the mathematician "sees two explanations"

On Wednesday, the Public Health Authority presented the first results of the antibody tests that were done earlier in April.

They show that Stockholm has the largest proportion of positive antibody tests: 7.3 percent, which can be compared with a total of 4.2 percent in Skåne and 3.7 percent in Västra Götaland. Nevertheless, the figures are much lower than the forecasts.

The numbers reflect the corona pandemic from week 15, as it takes a while before the body's immune system develops antibodies.

- It's not 7 percent now. We are somewhere at 20 percent plus in Stockholm, says state epidemiologist Anders Tegnell about the figures.

Math professor Tom Britton is one of those who estimated that Stockholm would achieve herd immunity as early as May.

When SVT asks him about the results of the tests, he is clear that both his own and FHM's previous forecasts diverge sharply, but that he also sees possible explanations for it.

- One explanation is that FHM's previous forecast was quite wrong, and mine too. The FHM reported that there was a lot of uncertainty about their previous forecast and that it would be accurate no one believed. But this is a big deviation. I'm doubtful.

- The other possibility is that the earlier forecast showed how many people would have been infected. Instead, the new prognosis is based on how many people have antibodies. Thus, everyone who is infected may not get antibodies, at least not at a level that can be detected by the tests, says Britton.

The possibility also sees the immunologist Petter Brodin:

- It may be that you have a mild infection and very weak measurable antibodies. This does not mean that you lack immunity, even if the antibody test is negative.

The results also show that it was most common with antibodies to covid-19 between the ages of 20-64 years. 6.7 per cent of the samples in this group were positive, which can be compared with 2.7 per cent in the 65-70 age group and 4.7 per cent in the 0-19 age group.

According to Anders Tegnell, this is a sign that the older group has managed to stay isolated to a greater extent, and that the spread is not as great among children.

The collection takes place over eight weeks and about 1,200 samples are collected each week.