It looked at mortality rates for the three conditions and found there were 48,168 deaths linked to Covid-19 with the virus being the underlying cause of death in three times as many deaths.
This meant Covid-19 accounted for 12.4 per cent of all deaths for the eight-month period.
There were a total of 13,619 deaths due to pneumonia and 394 deaths due to influenza.
Of the deaths where both influenza and pneumonia, and Covid-19 were mentioned on the death certificate, the underlying cause of death was coronavirus in 96 per cent of cases.
The ONS also looked back to when death records began being collected monthly and found Covid-19 remained more deadly than any flu and pneumonia seasons back to 1959.
There were more deaths due to flu or pneumonia in women but deaths from Covid-19 were 24 per cent higher in men.
Sarah Caul head of mortality analysis at the ONS said: “More than three times as many deaths were recorded between January and August this year where Covid-19 was the underlying cause compared to influenza and pneumonia.
“The mortality rate for Covid-19 is also significantly higher than influenza and pneumonia rates for both 2020 and the five-year average.
“Since 1959, which is when ONS monthly death records began, the number of deaths due to influenza and pneumonia in the first eight months of every year have been lower than the number of Covid-19 deaths seen, so far, in 2020.”
The ONS said the highest number of deaths due to influenza and pneumonia occurred in January, but deaths were below the five-year average in every month.
Deaths linked to Covid-19 were higher than deaths due to influenza and pneumonia between March and June.
The ONS said: “Age-standardised and age-specific mortality rates for deaths due to Covid-19 were statistically significantly higher than mortality rates due to influenza and pneumonia when compared to the five-year average and 2020 rates.
“The proportion of deaths occurring in care homes due to Covid-19 was almost double the proportion of deaths due to influenza and pneumonia (30 per cent and 15 per cent respectively).”