Spokesman Frederico Lombardi said the Pope was regularly surrounded by tens of thousands of people at audiences, Masses, greetings and other events.
He said it was unthinkable to create a wall between the Pope and the faithful.
Italian PM Silvio Berlusconi, himself recently attacked in public, warned of "hatred and extremism".
The Pope was not injured when Susanna Maiolo, 25, hurled herself at him in St Peter's Basilica at the Vatican but an elderly French cardinal standing nearby, Roger Etchegaray, suffered a broken hip.
The woman, who tried to throw herself at Benedict at the same Christmas Eve service one year ago, is now receiving psychiatric treatment and Mr Lombardi said he thought she would be dealt with very leniently by the Vatican.
'No hurt intended'
Father Lombardi said it was not realistic to think the Vatican could ensure 100% security for the Pope and that security guards appeared to have acted as quickly as possible.
"It seems that they intervened at the earliest possible moment in a situation in which zero risk cannot be achieved," he told the Associated Press news agency.
"People want to see him up close and he's pleased to see them closely too. A zero risk doesn't seem realistic in a situation in which there's a direct rapport with the people."
Vatican security officials would, the spokesman added, nonetheless review the episode and "try to learn from experience".
Mr Berlusconi, who is recovering from a violent attack in Milan earlier in the month, spoke to Italian TV after the attack on the Pope.
"We must really fight back against all these manufacturers of lies, extremism and hatred," he said.
It is still unclear what had motivated Ms Maiolo, who holds dual Swiss and Italian nationality.
She told doctors she had not wanted to hurt the pontiff, Italy's La Repubblica newspaper said in a report on its online edition.
The same paper quoted Cardinal Angelo Bagnasco, archbishop of Genoa and head of the Italian bishops' conference, as saying: "Nothing serious happened. It was a woman who tried to greet the Holy Father."
However, French Cardinal Paul Poupard, who was with the pontiff at the time of the incident, said it had been "definitely a threat to the Pope".
"With hindsight, you would say greater vigilance was needed, so those in charge of security should not let their guard drop even for a second," he added.
The Pope is protected by a combination of Swiss Guards, Vatican police and Italian police.
The most serious attack on a Pope in modern times was that on Benedict's predecessor, John Paul II, who was shot and seriously wounded by Turkish gunman Mehmet Ali Agca in 1981 as he rode in an open jeep in the Vatican .
Pope Benedict delivered his traditional Christmas message at the Vatican on Friday, appearing undaunted by the earlier incident.
As he emerged on to the balcony overlooking St Peter's Square, some observers said the Pope seemed unsteady on his feet, but he did not waver.
The German-born pontiff made no mention of the previous evening's incident during his Christmas Day message and prayers.
In his sermon to the world's 1.1 billion Roman Catholics, the Pope focused on the needy and praised the work of the Church in places like the Philippines, Korea and Sri Lanka.
Benedict has made it known he intends to carry out in full his schedule of engagements during the remainder of the Christmas and New Year holidays:
• He will appear at his study window overlooking St Peter's square to give his Angelus blessing to pilgrims at midday on Saturday
• After a repeat blessing on Sunday, he will attend a lunch with homeless people at a canteen run by a Catholic community in Trastevere, about 2km from the Vatican
• Next week, he will hold his customary Wednesday general audience inside the Vatican and on Thursday he will take part in a solemn end-of-year religious ceremony inside St Peter's
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