The WHO scientist, who is based in the offices in Venice, said he had decided to step down because the situation was becoming professionally “unsustainable”, the Guardian reported.
The decision came after he claimed he was pressured by a senior WHO official to hide the fact that Italy had not updated its pandemic plan since 2006.
Zambon said his resignation, first reported by TV station RAI, would take effect at the end of the month.
In August last year, investigations revealed that Italy’s pandemic plan was 14 years out of date, a factor that may have contributed to the high death numbers during the first wave of infections.
Italy was the European country that suffered the most at the beginning of the pandemic. Zambon was tasked with producing a report on the country’s response intended to provide information to countries that had not yet been affected.
Zambon’s report was published on the WHO’s website on 13 May but was removed a day later, allegedly at the request of the WHO’s assistant director-general for strategic initiatives, Ranieri Guerra.
Zambon later claimed in an interview with The Guardian that Guerra threatened him with dismissal unless he modified the part of the text relating to the outdated plan.
The WHO did not explain why the report had been removed but said in a statement in December that it “contained inaccuracies and inconsistencies”.