Stockholm's OMXS index rose 0.8 percent after five minutes' trading on Wednesday, in line with leading European markets, sending the index 0.2 percent higher compared to the turn of the year.
After 20 minutes of trading it had edged back down to 0.6 percent, but it is still an indication of a business world that is slowly recovering after one of the worst financial crises in recent years.
However, it still has some way to climb before it reaches the peak that came just before stock markets across the world plummeted at the end of February when the coronavirus pandemic hit.
The boost came when vaccine producer Moderna published research on a Covid-19 vaccine. But tensions between the US and China over Hong Kong caused concern, reported Swedish news agency TT.
Several Swedish companies presented their second-quarter reports on Wednesday.
Banking giant Handelsbanken released unexpectedly strong results, but generally low interest rates pushed down earnings, and it fell 1.6 percent on the stock exchange. Its rival SEB fell 2.6 percent.
Oil company Lundin Energy meanwhile rose 0.6 percent, and construction retailer Byggmax soared 5 percent after presenting a record-strong quarter – and its best sales in a single quarter ever for the company – thanks to the increase in home improvement projects during the coronavirus crisis.
Telecom giant Tele2 rose 4.1 percent on the Stockholm exchange after a strong quarterly report.