A mix of vaccines from AstraZeneca and Pfizer would speed up immunization of priority groups and could impact more than 16 million people, the study points out.

International clinical studies are beginning to confirm what some experts suspected: the efficacy and safety of applying different types of vaccines against COVID-19. Studies conducted by Oxford University in the United Kingdom and by the Instituto de Salud Carlos III in Spain indicate that the heterologous application of AstraZeneca and Pfizer vaccines, that is, the application of the second dose of the Pfizer vaccine after the application of the first dose of Pfizer AstraZeneca vaccine, would be responsible for producing an immune response superior to that observed with the application of two doses of AstraZeneca. 

Due to its efficacy, safety and protection, countries such as Portugal, Chile, Germany, France, Denmark, Sweden, Norway, Canada and South Korea already recommend the combination of AstraZeneca and Pfizer vaccines.

In Brazil, Anvisa still does not recommend mixing vaccines. An unprecedented study developed by the public health NGO ImpulsoGov points out, however, that the authorization of this measure can quickly avoid delays in vaccination in the country, given the prospect of offering vaccines in the country for the coming months.

The study points out that, according to Ministry of Health data, more than 180 million doses of Pfizer should be made available to the National Immunization Program by December this year, with an average of 33 million doses being received monthly from August. As for the doses of AstraZeneca, the forecast is that 96 million doses will be delivered to the PNI by December, half of the doses of Pfizer planned for the same period. It is noteworthy that, to date, 34.7 million people have been vaccinated with the first dose of Oxford-AstraZeneca vaccine and have not yet received the second dose.

For Marco Brancher, author of the study and data coordinator of the NGO ImpulsoGov, “Continuing the current pace of AstraZeneca vaccination (1.7 million doses per week), and considering the demand for a second dose, by the end of September we would need around 55 million doses in total. the Ministry of Health's schedule reveals that we should have only 38.2 million doses of this vaccine in this period. Thus, a possible solution would be to use doses of Pfizer as the second dose of AstraZeneca, for these 16.8 million people.” Using the same strategy to estimate what would be the minimum demand (second dose application) and demand for new doses of Pfizer, we conclude that given Pfizer's dose supply until the end of September (about 84.4 million doses) , it would be possible to accelerate the pace of vaccination with doses of Pfizer, apply the second dose to those who were vaccinated with Pfizer and still apply the second dose to individuals who were vaccinated with AstraZeneca, according to Brancher.

For João Abreu, executive director of the NGO ImpulsoGov, the effectiveness of vaccination is unquestionable, with more than 100,000 lives saved so far, according to studies by the organization. However, it is necessary to maintain the pace to achieve the desired collective immunity, which will not be possible if there is a shortage of doses for the second dose. Thus, the possibility of applying a second dose of Pfizer to people who took the first dose of AstraZeneca should be cleared by states and municipalities immediately. According to Abreu, "The measure can not only increase the level of protection of individuals, making the collective immunization strategy more effective, but also allows us to accelerate complete immunization in priority groups, which could end up losing the immunization window if we have a delay in the application of the D2 due to the low availability of AstraZeneca”. 

The municipality of Rio de Janeiro has already started the application of the second dose of Pfizer in pregnant and postpartum women who took the first dose of AstraZeneca. According to Álvaro Rossi, health consultant for the municipality of Rio de Janeiro, the strategy aims to allow for the acceleration of immunization in groups considered to be at higher risk. “Heterologous vaccination will bring us greater flexibility in the calendar, facilitating an eventual decrease in the time between the first and second doses in the coming months. This change would be fundamental to bring us closer to our goal of completely and safely immunizing everyone", says Rossi.

See the full study developed by ImpulsoGov below.

Press Information:

Luiza Amorim

Communication Manager



Learn about our methodology and access more tools

Simulate scenarios of the impact of vaccination on reducing deaths

We provide a spreadsheet for you to design and adapt the 3 scenarios outlined in our study on data and vaccination.

Access and see how the vaccination of priority groups directly impacts the reduction of deaths by Covid-19 in the country.

Calculate priority groups for vaccination in Brazil

We also used the available data to create a tool to assist in calculating the size of priority groups for Covid-19 vaccination.  

The spreadsheet shows the number of people in each priority group by state and municipality in the country, without double counting.

See how the webinar went

Part of these numbers and results were presented in a Webinar held on March 11, with the participation of Álvaro Rossi, Consultant to the US Department of Health, acting on the task force against Covid-19, and Marco Brancher, a specialist in health data which is focused on the Brazilian reality.

Faced with the progressive worsening of the crisis, the numbers have changed and the presentation shown in the Webinar has already had some numbers updated. The presentation updated on 23/03 is available for download on here.