The world champions extended their record unbeaten run to 37 games and, with just next week's tournament finale away to perennial challengers France remaining, England are on course to win an eighth straight Six Nations title and fifth consecutive Grand Slam.
England gave away a bonus point for a second straight match, with Italy scoring five tries.
Zoe Harrison's perfect run of 18 successful conversions came to an end when she failed to add the extras to Mia Venner's try, although the England fly-half was still on target with eight of her nine efforts.
John Mitchell's side ran in six tries before half-time to lead 40-19 at the break, with Packer and hooker Amy Cokayne both scoring twice as their forward power proved too much for the Azzurre.
'Unreal pack'
"I take my hat off to the pack, they were unreal," former England captain Packer told the BBC.
"All week we have been practising our set pieces and me and Amy were the lucky ones to dot the ball down but it was all of the girls' hard work."
But such is England's dominance Italy prop Silvia Torani was still pleased by her side's efforts.
"Someone told me it is the most points Italy have scored against England," she said.
"When you are playing first in the rank and World Cup winners, you have two options, play with fear or play with pride and I think today we did that, we didn't start well but we had the power and ability to change it.
"The result is a different story but I think at times you have to take performance over results."
Helena Rowland, lining up alongside England captain Megan Jones in midfield, marked her 50th cap with a try.
Despite missing more than a dozen players due to pregnancy, injury or post-World Cup retirement, England had cruised through their opening three games, beating Ireland before hammering Scotland and Wales.
They suffered a fresh setback shortly before Saturday's kick-off when back-row Maddie Feaunati was ruled out with a leg injury.
England still scored five tries in the opening quarter as they surged into a 33-5 lead against semi-professional Italy.
Italy hooker Vittoria Vecchini pulled a try back before Cokayne scored her second, again from a drive off her own line-out throw.
The hosts reduced England's lead to 33-12 with a penalty try after a deliberate knock-on by Ellie Kildunne, before the 36-year-old Packer crossed Italy's line again.
Abi Burton and Packer added further tries early in the second half before Italy secured a bonus point through Francesca Sgorbini's breakaway score, with the replacement also going over in the final minute.
In Saturday's other matches, France are away to Scotland with Ireland facing Wales in Belfast.