was in fine form as she returned to the movie set after contracting a breakthrough case of .
The actress, 36, was spotted filming the Boston Strangler in Cambridge, on Friday, just days after it emerged she and her family were battling the virus.
Though she admitted to feeling like 'rubbish' in the midst of her illness, Keira looked in good health as she threw herself into the character of Loretta McLaughlin, the groundbreaking reporter who broke the story of the Boston Strangler in the early 1960s.
Keira was dressed in costume as she stepped out onto the set, located on Lesley University.
The star wore a classic green coat, belted dress, black heels and floral scarf dangling around her neck.
Her short hair was given an elegant twist as it was styled into loose curls which framed her face with a side part.
At times, and in departure from her vintage look, she bundled up against the wintry weather with a large midnight blue jacket which fell to her knees.
A masked-up employee assisted Keira into her thick winter jacket, and the actress couldn't help but let out a relieved smile as she tossed on the extra layer of warmth.
Keira described her battle with COVID-19 in an interview with thewhich was published last weekend.
Double-jabbed Keira is married to Klaxons musician James Righton and they share two daughters, Edie, six and Delilah, two - who she revealed were faring better than her.
She said of her asymptomatic husband: '[He is] being very smug about it – he is convinced it’s because he’s one of those cold-water swimmers and I’m not.'
The actress admitted she was 'feeling pretty rubbish.'
A rep for the actress told that Keira and her husband were fully vaccinated and had finished their required 10 days in quarantine.
In October it was revealed that double-jabbed people still have a one in four chance of catching Covid from an infected household member, according to a study by 'Professor Lockdown' Neil Fergusson.
This is even the case if the person infected was fully jabbed themselves, in what is known as a vaccine breakthrough case, said Imperial College London researchers.
However, jabbed people recovered quicker from the virus, resulting in less severe and shorter symptoms. Being vaccinated also decreases a person's chance of getting Covid in the first place.