Survey exhibits results of Pfizer BioNTech vaccination within the UK

Researchers at Imperial College London in the UK have reported on the fifth round of the REACT-2 (REal-Time Assessment of Community Transmission-2) program – a cross-sectional community survey that assesses the prevalence of antibodies to the novel coronavirus with severe acute respiratory Syndrome was measured 2 (SARS-CoV-2) in adults in England.

The SARS-CoV-2 virus is the causative agent of the 2019 coronavirus disease (COVID-19) pandemic, which continues to pose a threat to global public health and has now killed more than 2.53 million people worldwide.

The fifth round of REACT-2 was conducted in the UK between January 26th and February 8th, 2021. The survey therefore included some people who had received a doses or two of a COVID-19 vaccine since the launch in December 2020.

Helen Ward and colleagues say the survey data showed that antibody positivity is unevenly distributed across the population, with prevalence being higher among key workers and some ethnic minorities – similar to the pattern seen during the first wave of the pandemic.

Confidence in vaccination is high overall, but lower in some of the higher prevalence groups, indicating the need for improved communication about perceived risks, the team said.

The researchers also say the data suggests that the optimal interval between the first and second dose may need to be tailored to specific populations.

A pre-print version of the paper is available on the medRxiv * server while the article is being peer-reviewed.

The SARS-CoV-2 infection rate is high in the UK

During the COVID-19 pandemic, the UK had a particularly high rate of SARS-CoV-2 infection, particularly among minorities and disadvantaged communities.

A vaccination program was launched in early December 2020, giving the elderly, healthcare workers and nursing homes priority over the first dose.

The introduction took place quickly. By the third week of February 2021, 15 million people in the country had received at least one dose of vaccine.

“There are early signs that the program, initially targeting people over the age of 70, health and care workers, older adults, nursing home residents and the most clinically vulnerable, is having an impact on hospital stays, mortality and possibly transmission,” says Ward and colleagues.

What did REACT-2 and the current study include?

The participants in the fifth round of REACT-2 completed questionnaires on demographics and COVID-19 vaccination history. They also performed a self-administered lateral flow immunoassay (LFIA) test to detect anti-SARS-CoV-2 immunoglobulin (IgG) antibodies.

Reconstructed epidemic curve from the number of symptomatic infections per week after onset in antibody-positive participants who report symptoms

Reconstructed epidemic curve from the number of symptomatic infections per week after onset in antibody-positive participants who report symptoms

People who were vaccinated had received either the Pfizer BioNTech or the AstraZeneca / Oxford vaccine. However, the current analysis focused on recipients of the Pfizer BioNTech vaccine, 12,820 of whom had received at least one dose.

The final survey cohort included questionnaire responses from 172,099 subjects, with valid IgG antibody results also being available for 155,172.

What were the results?

The overall prevalence of IgG antibodies was 13.9%. The prevalence was 37.9% in vaccine recipients compared with 9.8% in non-vaccinated individuals.

“The prevalence among vaccinated people reflects the recent introduction of the program. Many people received their first dose in the past three weeks and would not have had time to produce detectable antibodies,” say the researchers.

Among unvaccinated individuals, the antibody prevalence was among healthcare workers (21.9%), homeworkers (24.2%), blacks (22.4%), and Asians (20%) living in deprived areas (12.3%) ), higher. London residents (16.9%) and those aged 18 to 29 (14.5%).

Unadjusted antibody positivity up to 7 weeks after a single Pfizer BioNTech vaccination (aggregated by weeks) The lower panel shows the number of vaccines received, aggregated by the number of weeks since vaccine receipt.  The top graph shows unadjusted proportions of respondents who tested positive for antibodies, aggregated by the number of weeks since receiving the vaccine.  Binomial confidence intervals that were created using the Wilson method are shown.

Unadjusted antibody positivity up to 7 weeks after a single Pfizer BioNTech vaccination (aggregated by weeks) The lower panel shows the number of vaccines received, aggregated by the number of weeks since vaccine receipt. The top graph shows unadjusted proportions of respondents who tested positive for antibodies, aggregated by the number of weeks since receiving the vaccine. Binomial confidence intervals that were created using the Wilson method are shown.

An increased prevalence was also observed among key workers such as education (11.4%), public transport (12.2%) and other publicly accessible roles than among non-key workers (7.8%).

IgG positivity over time since single dose of Pfizer BioNTech vaccine by age and previous COVID-19 status.  The fields below show the number of vaccines received, aggregated by the number of weeks since the vaccine was received.  The upper charts show unadjusted proportions of respondents who tested positive for antibodies, aggregated by the number of weeks since receiving the vaccine, separated for those with no history of COVID-19 and those with confirmed or suspected COVID-19.  Binomial confidence intervals that were created using the Wilson method are shown.

IgG positivity over time since single dose of Pfizer BioNTech vaccine by age and previous COVID-19 status. The fields below show the number of vaccines received, aggregated by the number of weeks since the vaccine was received. The upper charts show unadjusted proportions of respondents who tested positive for antibodies, aggregated by the number of weeks since receiving the vaccine, separated for those with no history of COVID-19 and those with confirmed or suspected COVID-19. Binomial confidence intervals that were created using the Wilson method are shown.

Other unvaccinated groups with high antibody prevalence were people from Bangladesh (25.4%), Africa (23.4%) and Pakistan (21.9%).

“There is an uneven distribution of SARS-CoV-2 antibodies in the population, with greater exposure to key workers and some ethnic minority groups, similar to the pattern seen in the first wave,” write Ward and colleagues.

How safe were people when they were vaccinated?

Confidence in the vaccination was high overall (92.0%), but lower in some of the higher prevalence groups such as younger people and black people.

Particular concerns were about the way the vaccine worked, its long-term effects on health, pregnancy, fertility, allergies and comorbidities.

“To ensure that the vaccination program is implemented fairly for all walks of life, reporting on the benefits of the program – for the individual, family, contacts, and society at large – needs to be made easily available to diverse communities,” says Ward and the team .

More about the vaccinated people

Among 971 people who received two doses of vaccine, antibody positivity was high (91.1%) in all age groups, although it was lower in people over 80 years of age than in people under 50 years of age.

“This could be due to higher infection rates in younger years or possibly a decreased antibody response to vaccinations in the oldest people, which is consistent with some other vaccines,” suggest the researchers.

Among those who received a vaccine dose, 84.1% of those under 60 years of age tested positive for antibodies, with a decreasing trend seen with age. Among those with confirmed or suspected prior COVID-19, the post-dose prevalence of antibody positivity was 90.1% in all age groups.

The optimal time for the first and second vaccination may need to be adjusted

The team says the survey data suggests that the optimal interval between the first and second dose may need to be tailored to specific populations, with a longer interval may be more suitable for younger people and those with previous infections.

“Randomized trials to determine the optimal timing for first and second vaccinations are ongoing and, along with a growing body of evidence, will help make challenging prioritization decisions for national and international agencies,” the team concludes.

* Important NOTE

medRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guide clinical practice / health-related behavior, or be treated as established information.

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