A new observational study in Germany, recently published on the medRxiv* preprint server, found the Comirnaty vaccine to be 68.3% effective against COVID-19 for people over 80. In those fully immunized, the vaccine was found to be 73.2% effective in preventing hospitalization and 80.1% effective against death.
In clinical trials, the Pfizer-BioNTech (or Comirnaty) COVID-19 vaccine showed a 95% effectiveness against the vaccine. However, vaccine effectiveness in people over the age of 80 remained poorly understood because of low trial enrollment in this particular population.
Older people are at a higher risk of developing severe COVID-19 symptoms and dying from the virus. Given the results, the researchers suggest the Comirnaty vaccine provides high levels of protection for the elderly population.
How they did it
People 80 years or older from Bavaria, Germany, were enrolled in the study from January 9, 2021, to April 11, 2021. The Bavaria region has about 6.3% of inhabitants falling into this age bracket.
The average age of people in this study was 86.1 years, and 35.5% were male.
COVID-19 vaccination data was collected through the Bavarian Corona vaccination portal. The information included the type of vaccine, number of vaccine doses, gender, and age group.
Tests that were positive for COVID-19 infection or reinfection were confirmed with a PCR test and made public to the Bavarian Health and Food Safety Authority.
People in this age group were excluded from the study if they had COVID-19 that was not confirmed with a positive PCR test, the infection occurred before vaccination, the infection was related to hospitalization or mortality occurring before January 9, 2021, the vaccine was administered in 2020, or if the person was administered a vaccine other than Comirnaty.
Vaccination and infection rates among the elderly population
From April 11, 2021, about 63.8% of people over the age of 80 in Bavaria, Germany, received one dose of the vaccine and 52.7% received the second dose.
A follow-up of this patient population showed that about 11,228 tested positive for SARS-CoV-2. Thus, from the vaccination group, 1,148 people later tested positive for infection.
Of the vaccinated cases, 44.9% had one dose of the vaccine, and 55.1% were fully vaccinated.
The number of COVID-19 cases requiring hospitalization did not differ by whether someone was vaccinated or not. However, there was significantly less COVID-19 related mortality among vaccinated people than those that were unvaccinated.
Vaccine effectiveness leads to a lower risk of hospitalization and mortality
Two vaccine doses instead of one dose greatly reduced the risk of infection, becoming hospitalized, and dying from COVID-19.
Vaccine effectiveness after two doses in the elderly population was 68.3%. There was no difference in hospitalization or mortality between vaccinated men and women, indicating the COVID-19 vaccine is equally effective for both older men and women.
Women over the age of 80 who were unvaccinated were more likely to develop COVID-19 infection than unvaccinated men. However, unvaccinated older men who became infected were more likely to be hospitalized and die from COVID-19.
After the follow-up period, COVID-19-related hospitalization was 73.2%, and COVID-19 related mortality was 85.1% in the elderly population.
Strengths and weaknesses of the study
With the help of government data, the researchers obtained a large sample size. However, the researchers could not evaluate other risk factors beyond vaccination that could have contributed to an increased risk of infection in this population.
Another point to consider is the timing of the study. The research study took place before the new Delta variant became the dominant SARS-CoV-2 strain. Also, the immediate follow-up period made it less likely that antibody levels would be waning, suggesting vaccine effectiveness in the elderly population may not reflect today’s landscape.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.