The three-day, $3.74 million campaign, which ends on Sunday, was run by the Health Ministry, the United Nations Childrens' Fund (UNICEF) and the World Health Organisation (WHO) and is aimed at stopping polio before it spreads.
Angola this month identified three new cases of the disease - two in the capital, Luanda, and one in the western province of Benguela - the first cases since 2001.
The diagnoses, along with a new outbreak of polio in Indonesia, were a setback to the WHO, which has campaigned to stop the global spread of polio by the year's end.
In northern Bengo, a rural province that borders Luanda, health workers and parents were on high alert as medical staff in four-wheel drive vehicles travelled to the far corners of the region armed with oral polio vaccines.
"These two cases in Luanda have made us very concerned because Luanda is our neighbour, it is very close to us," said Zhenzo Makonda-Mbuta, head of Bengo's Public Health Department.
"Polio is very contagious. We don't want it here, so we need to react to make a barrier."
The immunisation scheme covers
less than half of the country
Angola's national routine immunisation coverage is just 45%, with coverage in remote areas particularly patchy as the health network struggles to rebuild following the end of 27 years of civil war.
The national offensive enlisted 12,500 teams to go house-to-house and visit markets and churches to make sure the vaccines reached the targeted five million children.
But news of the return of polio, a highly infectious disease that affects mainly the under-fives and can cause total paralysis in hours, had travelled fast. Most mothers were lining up to get their children immunised.
"We heard about the new cases on the radio, so we are very happy that these teams are coming here," said Lucia, whose 10-month-old daughter was vaccinated as they shopped in Bengo's capital, Caxito. "Every mother fears the return of polio and wants to protect her child."
"Every mother fears the return of polio and wants to protect her child"
In Luanda and Benguela, the campaign focused on stamping out the type-1 strain of polio, believed to have entered Angola from India.
"We imported very quickly a monovalent oral polio vaccine which is 90% effective in targeting this strain of the virus and was used only in areas where we have seen cases," said Mario Ferrari, UNICEF's representative in Angola.
New health scare
Elsewhere, the teams used a trivalent vaccine that produces antibodies to all three strains of the virus.
Ferrari said the partners were considering a third national immunisation round after a second planned for the end of August. Several doses of vaccine are needed to fully protect a child from polio.
Polio is the latest health scare to hit Angola, which this year fought an outbreak of the rare Ebola-like Marburg fever, which claimed more than 300 lives.