Angel station has twice been closed this week due to sickness and prioritising other stations, Transport for London said.
The size of the station means it cannot be left empty and Transport for London chose to prioritise keeping Old Street running due to its national rail link.
This week Angel - which is on the Northern Line - was closed on both Wednesday and Saturday.
The frequent closures of Angel have led to many asking on Twitter whether the station is closed before they attempt to use it.
Among the comments, one wrote: “Is there anything you can do regarding Angel station being closed almost once a week? Now it’s the whole weekend and massively annoying as we are [only made] aware at the last minute!”
Others added on Twitter: “Why does Angel station keep closing lately? Closed again today, no signs up to say why or for how long. Third time I've seen in the last few weeks. The northern line is running fine.”
“It's not temporarily unavailable when it happens two or three times every week, is it? It's just understaffing.”
“And why is it always Angel? I’ve known this happens on Sundays, but not midweek. There is no information at the station - can’t you even be bothered to put up a sign?”
Transport for London apologised to commuters for the disruption.
A statement from them read: “We apologise to Northern line customers for the disruption to their journeys, which was caused by Covid-related sickness over the past week.
“The closures on the Northern line have been minimised as far as possible and were done to prioritise nearby Old Street station, which is part of the same staffing pool and offers greater connectivity for customers.
“We strive to always exhaust all avenues before making the decision to close a station and the local team is working to minimise any future closures.”