Also, see the link below.

https://www.theguardian.com/world/2021/feb/25/pfizer-covid-vaccine-94-effective-study-of-12m-people-finds

important question. In relation to CoronaVac in Brazil, taking into account only a comparison between a proportion of people who developed symptoms between those vaccinated and those who took a placebo, the effectiveness would be 49.6% - below the 50% recommended as the minimum acceptable by the World Health Organization. So depending on the method of evaluating the results, these numbers can vary drastically

Dear Thyago Jose Arruda Pacheco and Dear Hermann Gruenwald Thank you for your contribution..

Dear Dr. Alemdar!

You spotted a critical issue. I argue the effectiveness rate is in general acceptable with regard to the vaccines of Moderna and Pfizer-Biontech. The product of Oxford is still under investigation: one cannot say at this point anything certain. The vaccines produced in China and Russia have clearly lower rate of effectiveness. The problem here is that at this moment countries do not have at their disposal enough vaccines and the delivery chains are slow. It can be stated that additional research is needed to find complementary measures for vaccinating:

Lobo-Galo, N., Gálvez-Ruíz, JC., Balderrama-Carmona, A.P. et al. Recent biotechnological advances as potential intervention strategies against COVID-19. 3 Biotech 11, 41 (2021). https://doi.org/10.1007/s13205-020-02619-1

Available at:Article Recent biotechnological advances as potential intervention s...

In addition people around the worlds are not that confident in the ability o COVID-19 vaccines to stop the pandemic:

Mohammad Hossain Shariare et al. (2020). The growing complexity of COVID-19 drug and vaccine candidates: challenges and critical transitions, Journal of Infection and Public Health, 15 December 2020, Article In Press, Open Access: Article The growing complexity of COVID-19 drug and vaccine candidat...

Yours sincerely, Bulcsu Szekely

Dear Bulcsu Szekely Thank you for your contribution.

I was not aware the effectiveness rate is so low. Good question.......I await the experts who may respond.

Dear Adita Thank you for your contributions.

Please take a look at the following RG links.

Preprint Estimating real-world COVID-19 vaccine effectiveness in Israel

Preprint Patterns of COVID-19 pandemic dynamics following deployment ...

Also, see the link below.

https://www.theguardian.com/world/2021/feb/25/pfizer-covid-vaccine-94-effective-study-of-12m-people-finds

Scientists from the medical center found that the vaccine was 85 percent effective at preventing symptomatic Covid-19 within 15 to 28 days after the shot was administered.

Please have a look at the following link:

https://www.statista.com/chart/23510/estimated-effectiveness-of-covid-19-vaccine-candidates/