[6] In that capacity, in 1990 he treated the first patient in Sweden with a viral hemorrhagic fever, believed to be a case to be either the Ebola or the Marburg virus disease.

[8] In an interview with Expressen, he describes his on-site work for the WHO with a Swedish expert team during the 1995 Ebola outbreak in Kikwit, Zaire as a formative experience.

[9] From 2002-03 he worked as a national expert for the European Commission to prepare, at the EU level, for public health threats such as anthrax, smallpox and other infectious diseases.

[6][2] Tegnell obtained a research-based senior medical doctorate from Linköping University in 2003 and a MSc in Epidemiology from the London School of Hygiene & Tropical Medicine in 2004.

As head of the Infectious Disease Control department at the agency, he had a key role in the Swedish large-scale vaccination program in preparation for the H1N1 swine flu pandemic,[2] which was declared by the WHO in June 2009.

[13] Tegnell was embroiled in controversy due to his role in the mass vaccination scheme of 5 million Swedes against swine flu, which caused about 500 children to develop narcolepsy.

[14][17][18] On 2 April 2020, while the COVID-19 pandemic was widespread in most Western countries, of which many had imposed quarantine measures, Canadian newspaper The Globe and Mail reported there were "no lockdowns, no school closures and no ban on going to the pub" in Sweden.

[22][23] Sweden's pandemic strategy has been described[citation needed] as trusting the public to act responsibly: instead of wide-ranging bans and restrictions, authorities advised people to remote work if possible, maintain good hand hygiene, and practice social distancing, while those over 70 were urged to self-isolate as a precaution.

Lena Einhorn contacted Tegnell in January 2020 to express her concern over the contagiousness of the virus, and said she was "exasperated" by the lack of measures in Sweden.

In the Alps and southern Europe, for example, there is no spread at all.Despite scepticism and criticism from a number of doctors and medical experts, as well as international news media, Sweden defended its strategy, with Prime Minister Stefan Löfven referring to "common sense" and Tegnell saying that the strategy is rooted in a "long tradition" of respecting "free will", as well as the high level of trust and respect Swedes have for public authorities.

[The economy] has the potential to start moving as usual very, very quickly once these things are over.....On 2 April 2020, Dagens Eko reported that significant spread of COVID-19 had occurred in retirement homes in at least 90 municipalities.

[34] Previously, the government and the public health authorities had strongly advised against external visits to retirement homes, with several municipalities outright banning them.

note: more than a third of Sweden's COVID-19 fatalities have been reported in nursing homes) of the disease and we had such a hard time controlling it in that setting.Tegnell's statements that the Public Health Agency was not pursuing a strategy of herd immunity have been challenged, however, after media uncovered email communication where he appears to confirm that herd immunity was indeed the chosen strategy.

King Carl XVI Gustaf and Prime Minister Löfven admitted they felt that Sweden's response was a failure due to the high number of deaths.