The warning came as hospitals in the country struggled to cope with the third wave of coronavirus.
Sweden, whose still mostly voluntary measures has made it an outlier in its response to the pandemic, has seen the number of people in intensive care rise to its highest level since the initial outbreak last year.
In some regions, intensive care has been filled to maximum capacity and the number of available beds for those worst ill is below 20% across the nation.
Minister for health and social affairs Lena Hallengren said: “There is no room now to start living as if the pandemic is already over.
“The infection rate does not go down by itself.”
Hallengren stressed the need to adhere to existing rules and recommendations but said she did not rule out stricter measures if the situation deteriorated.
She did not elaborate on what steps could be taken or what would trigger them.
On Wednesday, a total of 409 people were treated at intensive care units in Sweden, compared to about 560 at the height of the first wave of the virus.
Sweden, which has shunned lockdowns and kept schools, businesses and restaurants largely open, registered 7,510 new coronavirus cases on Wednesday and 38 new deaths, taking the total to 13,863.
The deaths reported have occurred over several days and sometimes weeks.
The country's death rate per capita is many times higher than that of its Nordic neighbours’, but lower than in most European countries that opted for lockdowns.
Data from the European Centre for Disease Control this week showed Sweden had among the highest number of new cases per capita in the EU during the last 14-day period and among the lowest deaths.
Sweden's health agency has said the relatively low death toll is due to vaccinations having a positive effect.
The country has administered 2.6 million doses, meaning 23.7% of the adult population has received at least one dose.
On Tuesday, officials said citizens under 65 who have had one shot of AstraZeneca’s COVID-19 vaccine would be given a different vaccine for their second dose.
Sweden paused the use of the AstraZeneca vaccine in March after reports of rare, but serious, blood clots among people who had received that shot.
It later resumed the use of AstraZeneca’s vaccine, but only for people aged 65 or above.
Chief epidemiologist Anders Tegnell said that the benefits of the AstraZeneca vaccine clearly outweighed the risks for people over 65.
Sweden also announced last week it would ease restrictions on those, mostly elderly, citizens who have had at least one vaccination shot against COVID-19.
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