In some CCG areas, as many as 84% of all people aged over 40 had received two doses of COVID-19 vaccine by 13 June, according to data published by NHS England.
In other areas, however, just over seven in 10 people aged over 40 had received a single dose of vaccine - and only just over half had received both doses.
The significant gap between different parts of England in vaccine coverage suggests that despite high vaccine coverage and rates of uptake nationally, parts of the country are far more exposed as cases of the Delta variant first identified in India rise.
An average of 9,365 cases of COVID-19 were recorded per day in the week to 17 June - matching levels last seen in February, and almost five times the level seen at the start of May. A total of 11,007 cases of coronavirus were recorded on 17 June, with more than 10,000 cases on each of the following two days.
Data from Public Health England (PHE) on 18 June show that '99% of sequenced and genotyped cases across the country are the Delta variant'.
PHE data suggests the Delta variant is linked to around 60% increased risk of household transmission compared to the Alpha variant - and shows that 'growth rates for Delta cases are high across the regions'.
Speaking at a Downing Street briefing last week, CMO Professor Chris Whitty highlighted the need to drive up vaccination rates in areas with lower coverage - pointing in particular to parts of London, where several CCGs have among the lowest coverage in the country.
Professor Whitty said: 'On London, let's start off with the glass half full. London, Londoners, as in the rest of the UK have shown great enthusiasm for vaccination. Overall the rates are higher than many countries would really dream of having at this point in time.'
But he said that although the rates of vaccination were still high in the capital, they were significantly behind other parts of the country.
He added: 'Some of this is mechanistic - it's because a lot more people move around in London, records and so on are less clear cut. There's a number of reasons why London, in common with other major cities in the UK, that always tends to have slightly lower rates of vaccination and screening.
'What we need to do is concentrate on these areas where the rates are lower, because we want to get all of them right up to the very highest rates which is what provides protections for individuals, and by being vaccinated someone provides protection for those around them.'
Prime minister Boris Johnson also admitted he was 'concerned' about London and that he hoped vaccination rates could be improved.
Analysis by GPonline shows that of the six CCG areas across England with the lowest proportion of over-40s to have received a first dose of vaccine by 13 June, five are in London. In Manchester CCG, 73% of over-40s had received a first jab, placing it second-lowest after North West London CCG.
The other four CCG areas in the bottom six are South East London, South West London, North Central London and North East London CCGs.
The same six CCGs had the lowest coverage of second-dose vaccinations among over-40s by 13 June - ranging from 59% to 54%. This is up to 30 percentage points lower than two-jab coverage in over-40s in the areas with highest coverage.
Liverpool, Salford and Leicester City CCGs are also in the bottom 10 nationally on the proportion of over-40s to have received a first dose as well as the proportion to have received a second dose by 13 June. Birmingham and Solihull CCG is in the bottom 10 for first-dose coverage, while Brighton and Hove CCG is in the bottom 10 for second doses in over-40s.
NHS North Staffordshire CCG has the highest coverage of first doses in over-40s, with 96% having received a first dose by 13 June, and 83% two doses. Stafford and Surrounds CCG recorded the highest level of two-dose vaccination, with 84% of all over-40s fully vaccinated by 13 June, and 93% having received a first dose.
Click through to GPonline's heatmap and charts for more detail on vaccination coverage by CCG, and visit our COVID-19 vaccine tracker for more information on the vaccination campaign nationally.