That's what some doctors believe ... saying the lack of a Super Bowl parade in S.F. last month helped slow the spread of COVID-19 in Northern California tremendously.

"It may go down in the annals as being a brutal sports loss," chair of UC San Francisco department of medicine, Dr. Bob Wachter, told the Wall Street Journal this week, "but one that may have saved lives."

The Bay Area reported its first cases of coronavirus in the days -- and hours -- leading up to the 49ers-Chiefs game in early February ... and if SF had beaten KC in The Big Game -- it could have had disastrous results.

Doctors say a Super Bowl party on the streets of San Francisco might have led to a massive spread of the coronavirus ... killing hundreds, if not thousands.

"It is certainly hard to imagine a more high-risk situation," UCSF COVID-19 expert Dr. Niraj Sehgal told the WSJ.

Of course, the Niners weren't able to beat Patrick Mahomes down in Miami -- Garoppolo just missed the game-winning throw -- and the Super Bowl party ended up in Kansas City.

And, with KC not reporting its first cases of the virus until mid-March ... they were able to party hard without consequences.

So ... thanks, Garoppolo!