The by-election was triggered after a councillor faced claims he shared "racist" comments on social media.
Read moreHarlow District Council
By Laurence Cawley
BBC News, East
Vaccine rollout key to Tory success in Harlow
Copyright: Getty ImagesImage caption: Broad Walk, Harlow, Essex (archive picture) Concerns about bin collections and the state of the high street are believed to be behind the collapse of Labour's control of the council in Harlow, Essex.
Divisions among Labour councillors also caused concern among voters, it is reported.
But campaigning Conservatives in the area said the vaccine programme came up repeatedly on doorsteps, suggesting the success of the roll-out was a major factor in Tory success.
The Tories also seized Redditch and Nuneaton & Bedworth councils in the Midlands from Labour and saw heavy losses across North East local authorities overnight.
Ballots continue to be tallied up across England, Scotland and Wales following the Super Thursday polls - the largest test of political opinion outside a general election.
Harlow: Conservative MP, Robert Halfon, 'proud' of win
Harlow MP, Conservative Robert Halfon, said he was "proud" that the Tories had seized control of the Essex district, tweeting that the authority was now under Conservative control for "only the second time in the history of our town".
Mr Halfon also offered "commiserations to the many hard-working" Labour councillors who had lost their seats.
"Whatever our significant political differences, all political parties want to build an even better Harlow and help people through Covid," he said.
Harlow: Former Labour leader 'disappointed'
The former Labour leader of Harlow Council has said he is ""disappointed" about both losing his seat and his party losing control of the authority to the Conservatives.
Labour held onto just one of the seven seats it was contesting.
Mark Ingall said: "I am proud to have served as a Labour councillor and proud to have represented Bush Fair."
Harlow District Council: Conservative gain
Andrew Sinclair
BBC Look East political correspondent
The Conservatives have taken control of Harlow District Council from Labour.
Labour held onto just one of the seven seats it was contesting.
Council leader Mark Ingall has lost his seat.
Copyright: BBCHarlow: Could be a close result?
Andrew Sinclair
BBC Look East political correspondent
Counting proper is now under way in Harlow and the contest is said to be very close in several seats.
Labour currently runs the council but a very good night for the Tories could see them take it.
Copyright: BBCIn fact, the first ward has already been declared and it's a win for the Conservatives, taking the seat from Labour.
Harlow: Turnout just over 32%
The returning officer has told everyone at the Harlow count that the verification - counting the number of ballot papers - is complete.
The votes now being counted are in the 11 wards for the Harlow Council election and the three Harlow divisions in the Essex County Council election.
The counting of votes for the Fire, Police & Crime Commissioner for Essex will take place on Saturday.
Turnout for this election is just over 32%, the officer said.
Harlow District Council: Current situation
Copyright: GoogleHarlow District Council is responsible for services like bin collections, parks, public housing and local planning applications.
Party in power: Labour
Seats up for election 13
Seats on council: 33
Other public services are controlled by Essex County Council which covers a wider area.
Harlow will be a council to watch
Simon Dedman
BBC Essex political reporter
Harlow is a classic red-blue bell-weather ding dong council.
Labour has a pretty good majority on that council and on the face of it you would think it would be quite hard to lose there.
But on the county council elections last time around, the Conservatives took all the Harlow seats up for grabs.
It is definitely one of the Essex councils to keep an eye on.