The figure was hit on 21 April, just ahead of the vaccine rollout extending to 44-year-olds in England.
Cllr Evelyn Akoto, cabinet member for public health and community safety at Southwark Council, congratulated all those who have received the vaccine.
"[It is] truly a momentous moment for them and the entire borough in our collective efforts to beat the virus.
"I would like to thank the incredible NHS staff, volunteers, and council colleagues who continue to work tirelessly to make sure all our communities feel confident in benefitting from the protection the vaccine offers.
"With every vaccination, we step towards living life more fully, more safely and with fewer restrictions. I encourage all residents to take up the opportunity to have the vaccine when offered," she said.
Dr Nancy Küchemann, GP and clinical lead at NHS South East London Clinical Commissioning Group (SEL CCG), said: "This is now also a much larger number of residents who have been vaccinated than were infected by the virus and the vaccine will give significant protection to those most at risk.
"I urge eligible people in Southwark to book in for their vaccination as soon as they can while continuing to follow public health guidance to reduce transmission and help save lives."
On Monday around half a million 44-year-olds are set to receive a text inviting them to get their jab through the national booking service.
It is the first time the vaccine rollout has been extended by a single year in England – the NHS said it would set out when people aged 40 to 43 will be able to book an appointment in the coming days.
The NHS has been prioritising second doses throughout April in response to supply constraints.