The former prime minister, who was in power from 2010 to 2016, said that ministers focused too heavily on a possible influenza pandemic.
Instead, they should have broadened preparations to include all respiratory illnesses, saying “more should have been learned” from Sars in 2002.
Like Covid, Sars was a new contagious coronavirus. Influenza is also a contagious respiratory illness, but of a different family of virus.
The government has repeatedly been criticised for not preparing the UK for a new and unknown disease.
Speaking to the national security strategy committee, Cameron said: “I think the mistake that was made was that in thinking about future pandemics, the focus was very much on influenza rather than on respiratory diseases and I think that is where, and I am sure there will be a big inquiry into what we learn and all the rest, but I think there was a pretty good flu pandemic plan but it was a flu plan rather than a respiratory illnesses plan.”
Cameron said his government had “set up a unit in the Cabinet Office to do sort of global virus surveillance” but he was “not quite sure what happened to that”.
He added: “But [...] more should have been learned from the experience with Sars and the respiratory diseases in terms of our own preparedness. But I wouldn’t blame the national security architecture for that. The architecture was there.”
A 2016 drill, called Operation Cygnus, was aimed at testing UK resilience. It exposed how hospitals and care homes faced being overwhelmed should a new virus hit the UK.
It was criticised for failing to check up on supplies of personal protective equipment (PPE), capacity for testing and the number of ventilators.
MPs also uncovered last year that that it failed to make any recommendations to Treasury or business officials.
Amid rumours that former US president Donald Trump was considering a return to politics, Cameron was also asked if he would consider a comeback.
“No,” he said. “Thinking about Donald Trump making a comeback is enough to keep us all spinning over.”
Cameron also defended holding the 2016 Brexit referendum, which ended his premiership, saying it was “properly thought through” before the 2015 general election.
The ex-PM also used his appearance to criticise decisions taken on security and aid by his successors.
He said Theresa May made a “very bad mistake” allowing the role of cabinet secretary and national security adviser to be merged, with Mark Sedwill holding both roles during her tenure in Downing Street.
“I think it was for instance a very bad mistake combining cabinet secretary and national security adviser – they are two jobs,” he told the committee.
“For one person, even if you were a cross of Einstein, Wittgenstein and Mother Teresa, you couldn’t possibly do both jobs and I think that temporarily weakened the National Security Council.”
On Boris Johnson’s decision to scrap the Department for International Development (DfID), Cameron said: “I think abolishing DfID is a mistake too for all sorts of reasons but one of which is actually having the Foreign Office voice around the (National Security Council) table and the DfID voice around the table I think is important – they are not necessarily the same thing.
“Can you really expect the foreign secretary to do all of the diplomatic stuff and be able to speak to the development brief as well? That’s quite a task, so I think it is good to have both.”