Richer countries have surged ahead with inoculating their population, but many poorer countries are still awaiting their first vaccine doses.
The government has pledged to strengthen security in zones deemed high risk.
Italian Foreign Minister Luigi Di Maio has called on the UN to carry out a full investigation.
The West African nation has recorded 80,759 Covid-19 cases and 582 deaths since the start of the pandemic.
China has donated 200,000 Sinopharm vaccine doses to the southern African country.