SARS-CoV-2 vaccines from Pfizer-BioNTech and AstraZeneca reduce mortality in the elderly

Researchers in the UK have demonstrated the effectiveness of Pfizer-BioNTech and AstraZeneca vaccines against the Severe Acute Respiratory Virus Coronavirus 2 (SARS-CoV-2) in preventing the death of the elderly with Coronavirus Disease 2019 (COVID-19).

Analysis of more than 48,000 people aged 70 and over found that COVID-19 cases vaccinated with a dose of Pfizer BioNTech’s BNT162b2 vaccine had a 44% lower risk of death compared to those who were not vaccinated Had vaccinations with one dose of AstraZeneca’s ChAdOx1 vaccine had a 55% reduced risk.

The Public Health England team in London also found that cases given two doses of BNT162b2 reduced the risk of mortality by 69% compared to those who were not vaccinated.

The researchers say the study is the first to assess the effectiveness of ChAdOx1 in preventing mortality and that a single dose provides a level of protection similar to that of a dose of BNT162b2.

“We found that confirmed cases of COVID-19 vaccinated with either a single dose of BNT162b2 or a single dose of ChAdOx1 had a significantly lower risk of death compared to non-vaccinated cases,” write Jamie Lopez and colleagues.

However, the second dose of BNT162b2, which provides even more protection, underscores the importance of completing the full two-dose regimen, the team added.

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

The evidence on the effectiveness of the vaccine in preventing mortality is limited

Studies of the actual effectiveness of vaccines against SARS-CoV-2 have reported high levels of protection against both symptomatic COVID-19 and asymptomatic diseases.

However, evidence of effectiveness against the most severe outcome – mortality – is currently limited and has not yet been reported for most vaccines, Lopez and colleagues said.

The UK was the first country to introduce a COVID-19 vaccination program. This started with the administration of Pfizer-BioNTech’s BNT162b2 vaccine in December 2020, followed by the launch of Oxford-AstraZeneca’s ChAdOx1 vaccine from March 2021.

Older adults, nursing home residents, and health and social workers were the first to be prioritized for vaccination and later introduced in increasingly younger age groups and clinical risk groups.

At the start of the vaccination program, policy makers decided to increase the interval between the two vaccine doses from 3 to 12 weeks in order to maximize the number of high-risk people who could be offered the first dose.

“Early data suggest that a single dose of BNT162b2 was 80-85% effective in preventing mortality in those over the age of 80,” write Lopez and colleagues. “However, the effectiveness of ChAdOx1 against mortality has not yet been reported.”

What did the researchers do?

A community COVID-19 testing program is available in England for those who report symptoms (such as high temperature and persistent cough), for residents and employees of care homes, and for those taking local or national asymptomatic tests.

Lopez and colleagues linked any new symptomatic cases positive for SARS-CoV-2 infection by polymerase chain reaction (PCR) to mortality data from National Health Service (NHS) records.

Percentage died due to vaccination status (a) 70-79 year olds (b) 80+ year olds

Percentage died due to vaccination status (a) 70-79 year olds (b) 80+ year olds

Test and mortality data between December 8th (when vaccination began) and April 17th were extracted and a survival analysis was performed to estimate the risk of death within 28 days of a positive PCR test.

The mortality risk was assessed as COVID-19 in 48,096 people aged 70 and over. Of these COVID-19 cases, 79.1% were not vaccinated, 12.7% were vaccinated with BNT162b2, and 8.2% were vaccinated with ChAdOx1.

What did the study find out?

In people 80 years of age and older for whom at least 28 days of follow-up data were available, 16.1% of those who were not vaccinated died compared with 9.2% of those who were vaccinated with a dose of BNT162b2 and 11.3% of those who did one dose of ChAdOx1 vaccinated individuals and 4.7% of those vaccinated with two doses of BNT162b2.

Among 70 to 79 year olds with at least 28 days of follow-up data, 4.0% of those who were not vaccinated died compared with 2.7% of those who received a dose of BNT162b2, 2.1% of those who did vaccinated with one dose of ChAdOx1, and 0.0% of those vaccinated with two doses of BNT162b.

None of the subjects had 28 days of follow-up data after two doses of ChAdOx1 due to the later introduction of this vaccine.

Survival analysis estimated that people vaccinated with one dose of BNT162b2 were 44% less likely to die of COVID-19 than those who were not vaccinated, while those vaccinated with one dose of ChAdOx1 were 55% less likely to die died and people vaccinated with two doses of BNT162b2 were 69% less likely to die.

What did the authors conclude from this?

The researchers say the results provide strong evidence that both the BNT162b2 and ChAdOx1 vaccines provide high levels of protection against COVID-19 mortality after a single dose.

This finding supports the prioritization of the first dose in risk groups associated with a high incidence of diseases and restrictions on the delivery or dispensing of vaccines.

“Nevertheless, a second dose of BNT162b2 offers further protection against mortality and underscores the importance of completing the course,” 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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