Understand how the booster dose against Covid and 2nd dose of Janssen will be

Last Tuesday (16), the Minister of Health, Marcelo Queiroga, announced that all people aged 18 or over will receive a booster dose of the Covid vaccine. In addition, he stated that Janssen’s immunizing agent, before a single dose, is now used in two doses, like other vaccines being applied in Brazil.

The change brought a lot of confusion regarding deadlines and the type of immunizing agent used, surprising even Anvisa (National Health Surveillance Agency) and Janssen, who were not consulted.

The application of the new injection should take place five months after the second dose of any immunizing agent. In the case of Janssen, people who already took the first dose two months ago can take the second and, after five months, they will then receive a booster dose.

Regarding the type of immunizing agent used, the paste reinforces that heterologous vaccination, that is, with an immunizing agent different from that used in the first doses, is the preference for the third dose.

Please ask your questions below about the Janssen booster and second dose.

Who can get a booster dose of Covid vaccines now?

All people aged 18 and over can have a booster dose of Covid vaccines, regardless of what type of immunizer they received in the first vaccination course. The application of the booster dose should be done five months after the second dose — before, the orientation was to wait six months.

The new Health guideline, to extend the booster dose to the entire adult population, differs from what Anvisa has decided so far. The regulatory agency provides for the time being the booster dose for seniors over 60 years, immunosuppressed and health professionals.

What type of immunizer is used?

According to the Ministry of Health, the third dose will be with a heterologous scheme, that is, with an immunizing agent different from the one that was applied initially. The choice is based on a study conducted by the paste itself, which indicated a greater protection of the reinforcement in this scheme. The priority will be to use doses from Pfizer and, in the absence of this immunizing agent, AstraZeneca or Janssen.

When will the application be available?

Despite the federal orientation, the calendar varies between states and cities, as has already happened in other moments of the campaign against Covid. The population needs to be aware of the schedule of the place where they live. In the state of São Paulo, for example, the additional dose will be applied as of this Thursday (18).

How have other countries done?

The third dose (also called booster, its name in English) has already started in several countries for adults aged 18 and over. In the United States, since September, people over 65 years old who took the Moderna vaccine, those over 18 years old with high risk or those over 18 years old with high exposure due to their profession can take an additional dose. Previously, the Food and Drugs Administration (FDA) only recommended the additional dose for people 65 years of age or older or immunocompromised.

In Europe, the EMA (European Medicines Agency) recommended, in early October, a third dose of mRNA vaccines for immunocompromised people, but each country can autonomously decide on the booster dose for the entire population.

Last Friday (12), the Netherlands decreed a new three-week lockdown. Austria also started, last Saturday (13), a lockdown for the unvaccinated, who are prevented from going to places like bars and restaurants, for example. The idea is to encourage people to take the Covid vaccine.

If vaccines protect against the disease, why do I need a booster now?

The most recent studies point to a drop in one of the types of protection afforded by vaccines from six to eight months after application. However, despite being expected, the drop in the amount of antibodies with any type of immunizing agent tends not to be reflected in the protection against severe cases and death. For this, protection tends to be longer lasting and remain high.

Data from some countries, such as Israel and the United Kingdom, show that, six months later, the effectiveness of Pfizer and AstraZeneca vaccines dropped from 90% to 65%, in the case of Pfizer, and from 65% to 45%, for AstraZeneca .

However, protection against hospitalizations and deaths remained high — it went from 99% to 90% in the case of Pfizer. For AstraZeneca, regarding hospitalizations, it was 95% to 75% and, for deaths, 95% to 80%.

Recently, the UK government released new data on the effectiveness of a booster dose of Pfizer or Moderna in individuals who received the primary regimen with AstraZeneca or Pfizer. Regarding the defense against symptomatic cases of Covid, vaccines showed a drop in protection in this group five months after the second dose in people aged 50 years and over.

The third dose, however, raised protection to above 90% in both cases, with the risk of contracting the disease decreasing almost tenfold from two to six days after the booster dose compared to the period just before the injection.

Thus, booster doses are not only able to recover a fall in natural immunity to symptomatic Covid infections, but also significantly decrease the risk of further hospitalizations and deaths within five to six months after vaccination with the primary regimen.

I took two shots of AstraZeneca, do I need a booster shot?

Yes. The ministry’s guidance is to apply the booster dose, preferably with the immunizing agent from Pfizer, five months after the second injection.

Studies have already pointed out that a heterologous AstraZeneca/Pfizer vaccination produces a longer lasting and also stronger immune response. A study conducted by the ministry itself showed that Pfizer’s messenger RNA vaccine showed a better immune response in the booster dose than viral vector vaccines such as Janssen and AstraZeneca.

I took two shots of Pfizer, do I need a booster?

Yes. Health guidance is to apply the booster dose, preferably with AstraZeneca or, failing that, Janssen, five months after the second injection.

Regarding the Pfizer vaccine, international studies also support an increase in the protection provided by antibodies and defense cells with a third dose of the same immunizing agent, which is why it is also an option.

I was vaccinated with Janssen’s single dose vaccine. Why do I now need a second dose and a booster?

Janssen’s single-dose vaccine has an efficacy of 66% for symptomatic cases of Covid-19, a rate that jumps to 94% when two doses are used. For this reason, experts and authorities started to recommend the new scheme.

According to the Ministry of Health, all adults who took Janssen for at least two months must receive a second injection. After the application of the second dose, the period to receive the booster dose is from five months, and the booster should be with Pfizer or AstraZeneca.

My first dose was one immunizer and the second one another. Do I need backup? With which vaccine?

Yes. According to Saúde, people who have already taken a heterologous vaccine between the first and second dose should receive a third dose from Pfizer.