A preprint published in MedRxiv by Ward and others on 26th February 2021 reviews this.

The vaccination programme which began in England in December 2020 gave priority to administering the first dose to the largest number of older individuals, health care and care home workers. 

It is known that England has experienced high rates of SARS-CoV-2 infection, particularly affecting minority ethnic groups and more deprived communities.  

This study undertook a cross sectional community survey in England between
26th January and 8th February 2021 as the fifth round of the real time assessment of community transmission, the REACT2 programme. 

Participants completed questionnaires, including demographic details and clinical and COVID-19 vaccination histories and self-administered a lateral flow test to determine IgG against SARS-CoV-2 spike protein. 

There were sufficient numbers of participants to analyse antibody positivity after
21 days from vaccination with either the Pfizer or the AstraZeneca vaccine. 

Results showed that the survey comprised of 172,099 people with valid IgG antibody results from 155,172 of them. 

The overall prevalence of antibodies in England was 30.9% with 37.9% in the vaccinated and 9.8% in the unvaccinated group.  

The prevalence of antibodies in unvaccinated people was highest in London at 16.9% and higher in people of black origin 22.4% and Asian ethnicity at 20% compared to white race at 8.5%.  

The updated vaccination by age was highest in those aged 80 years or older at 93.5%.  Vaccination confidence was high with 92% of people saying that they had accepted or intended to accept vaccination. 

Vaccine confidence varied by age and ethnicity with lower confidence in young people and those of black race. 

Particular concerns were identified around pregnancy, fertility and allergies. 

In 971 individuals who had received two doses of the Pfizer vaccine, the proportion testing positive was higher across all age groups. 

Following a single dose of the Pfizer vaccine after 21 days or more, 84.1% of people under 16 tested positive with a decreasing trend with increasing age but high responses to a single dose in those with confirmed or suspected prior COVID-19 infection at 90.1% across all age groups. 

The study concluded that there is an uneven distribution of SARS-CoV-2 antibodies in the population with a higher burden in key workers and some minor ethnic groups, similar to the pattern in the first wave. 

Confidence in the vaccine programme was high overall although it was lower in some of the higher prevalence groups, which suggested the need for improved communication about specific perceived risks. 

Two doses of the Pfizer vaccine or a single dose following previous infection conferred high levels of antibody positivity across all ages.  

The analysis was limited to the Pfizer vaccine as there was insufficient data for comparison to the AstraZeneca vaccine.  

The data suggested the optimum interval may need to be tailored to population groups, with a longer delay in second doses more appropriate for younger age groups and those with prior infection.  

In addition, it is important to establish the relationship between antibody positivity following vaccination and the subsequent risk of hospitalisation and/or death in order to assess whether antibody response is a useful correlate of protection. 

Initial data from a cohort of UK health workers suggests a single dose of Pfizer vaccination is associated with a 72% reduction in infection after 21 days. 

In studies of individuals 80 years or over, a single dose of vaccine is associated with a greater than 50% reduction in cases some 28 days after vaccination, rising to 98% after second doses were given. 

This emphasises the importance of second doses particularly in the older population. 

The London General Practice commends the government on its vaccination programme rollout and looks forward to all populations being vaccinated appropriately.

Dr Paul Ettlinger

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