Registration for those born between 1957 and 1961 opened at the stroke of midnight on Tuesday.
A day earlier, people born in 1955 and 1956 were allowed to sign up, following in the footsteps of the 67-69 age group, which became eligible earlier this month.
All citizens in these age groups will receive a vaccine developed by drug maker AstraZeneca, according to officials.
People can send a text message to sign up for a shot. They can also go online to register or call a 989 vaccination hotline to schedule an appointment.
Direct reservations at vaccination sites are possible, but officials have advised people against visiting in person to limit the risk of exposure.
Prime Minister Mateusz Morawiecki last week encouraged Poles to vaccinate themselves against COVID-19 using the AstraZeneca shot.
The European Medicines Agency (EMA) said on Thursday the vaccine was “safe and effective.”
The European Union's drug watchdog told an online news conference it was convinced the benefits of AstraZeneca's vaccine outweighed the risks following an investigation into reports of blood disorders that prompted more than a dozen nations at one point to suspend its use.
Poland hopes to vaccinate 60 to 70 percent of its population against the coronavirus by the autumn, Health Minister Adam Niedzielski has told the media.
On Monday, a fresh supply of around 507,000 doses of the Pfizer-BioNTech COVID-19 vaccine arrived in Poland, Michał Kuczmierowski, head of the Government Strategic Reserves Agency, told reporters.
A day earlier, Poland received about 210,000 doses of a coronavirus vaccine developed by US drug maker Moderna, Kuczmierowski added.
On Friday, a shipment of around 65,000 doses of the AstraZeneca shot reached the country, according to officials.
Frontline healthcare workers were first in line to be inoculated in Poland, followed by nursing home residents.
Other priority groups include the elderly, people with chronic health conditions, teachers, police, and soldiers.
Poland last week began administering COVID-19 vaccines to cancer patients and people suffering from various chronic diseases.
On March 29, vaccinations are set to start for police officers and military and law enforcement personnel.
More than 6,000 vaccination sites are available to citizens as the country rolls out its COVID-19 inoculation programme, according to the prime minister's top aide, Michał Dworczyk, who is spearheading the drive.
Michał Dworczyk, the man in charge of Poland's COVID-19 vaccination campaign. Photo: PAP/Aleksander Koźmiński