RIO DE JANEIRO, BRAZIL – In cities of at least 18 states, doses to complement immunization with the Butantan vaccine are scarce, an issue that may have an impact on protection against Covid-19.
By early Monday, May 3rd, the administration of the second dose of the Coronavac, a crucial vaccine in the Brazilian immunization program against Covid-19, was suspended in at least 9 capitals cities and hundreds of other cities in 18 states.
The suspension of vaccination is not exactly new in Brazil, having occurred in several states in the past. However, previously, the appointment of new priority groups was interrupted – the second dose administration continued, because it had been reserved.
Now the vaccine is also scarce for those who had been administered the first dose. This, coupled with the fact that hundreds of thousands of Brazilians have not returned to complement immunization with the Coronavac, is a concern for experts.
According to a survey conducted in late April by the National Confederation of Municipalities (CNM), almost a third of Brazilian cities have run out of the second dose of Coronavac. The situation is more serious in the country’s Southern region – there, nearly half of municipalities said they had interrupted vaccination with the second dose.
According to experts and the current management of the Ministry of Health, the cause of this crisis is a March communication from the federal Health Ministry stating that the second doses need not be saved for application in people who had been vaccinated with the first dose, because supply was contractually guaranteed.
The Coronavac is produced by Chinese pharmaceutical company Sinovac in partnership with the Butantan Institute in São Paulo. Currently, about 3 out of every 4 people vaccinated in Brazil have received the immunizer.
Why is the second Coronavac dose so important?
Two vaccines are currently used in Brazil: the Coronavac and AstraZeneca’s immunizer, developed in partnership with Oxford University and produced in Brazil by the Oswaldo Cruz Foundation (Fiocruz).
The AstraZeneca-Oxford vaccine requires a second dose to be administered within a 3-month interval. But the Coronavac vaccine has been proven to be more effective when the second dose is administered at an interval of between 21 and 28 days.
A recent study in Chile showed that the Coronavac is only 16% effective after the first dose. The study, which analyzed the vaccine’s effectiveness among 10.5 million people, found that protection against the symptomatic form of the disease increased from 16% to 67% with the second dose. By way of comparison, AstraZeneca’s vaccine is 76% effective 2 weeks after the first shot.
The efficacy rate for people who have only had one shot is low, at 16% – that is, out of 100 people who had contact with the virus after one shot, 84 became infected and developed symptoms.
The efficacy rates for cases that require hospitalization in wards (35.65%) and in ICUs (42.70%) are higher, but are still considered low protection. In the case of Covid-19 deaths, the efficacy rate with only one dose stood at 40.23%.
The Chilean study’s conclusion was clear: just one Coronavac dose is not enough to protect against coronavirus infection.
“Efficacy with a single dose is low. That’s why we have to insist that everyone take the second dose to ensure an adequate level of protection,” says Butantan Institute research director Ricardo Palácios.
Uncertainty about a long delay in the second dose
The vaccine efficacy data are based on protocols, and according to experts it is unclear what may happen if people exceed the 28 days scheduled for the second dose too long.
In other words, there is no data yet on the difference in efficacy rate with delayed shots. There is only certainty regarding Coronavac: only one dose does not ensure immunization.
According to the Ministry of Health’s April 27th recommendation, those who have not had their second shot within 28 days should still receive it.
“It is unlikely that increased intervals between vaccine doses cause a reduction in the efficacy of the vaccination scheme,” reads the text.
Experts say that delays should be prevented, because protection is not assured until the second dose is administered.
In April 28th, at a press conference, the Butantan Institute director Dimas Covas said that even if a person takes the second dose 15, 20 or even 30 days after the scheduled date, there is no interference in the vaccination scheme.
The source of the crisis
In a statement last Friday, the Butantan said it had “no responsibility for the delay in the administration of the second Coronavac dose.”
“The Butantan produces and delivers the Covid-19 vaccine to the Ministry of Health, which is responsible for planning and distribution,” the institute said on Twitter. “So far, the Butantan has performed its deliveries in compliance with the contract it has undertaken. The programming to use the second dose stock to administer the first dose is up to municipalities, based on guidance from the Ministry of Health.”
Experts point out that the Ministry of Health failed to follow epidemiologists’ advice to stockpile vaccines that require two doses to ensure complete immunization.
According to the current Health Minister himself, Marcelo Queiroga, changes in the Covid-19 vaccination strategy in the management of his predecessor, Eduardo Pazuello, contributed to the current vaccine shortage in several Brazilian states.
A survey by the newspaper O Globo showed that municipalities in at least 18 states suspended the administration of the second dose of the Coronavac. According to the newspaper Folha de S. Paulo, more than half of the country’s capitals are short of Coronavac, and 7 others have a limited availability of the immunizer.
In February, Minister Pazuello announced that cities should use the entire first dose stock, and not worry about the second. The Ministry of Health reversed its decision a few days later: the second dose should be stored. But only one month later, the Ministry said again that all the vaccines stored to guarantee the second dose could be used as the first dose.
On April 26th, Queiroga said in the Senate that guidelines had changed and that his Ministry recommends now that the states store half of the stock for the administration of the second dose.
Another issue was the shortage of raw materials from China, which led to a halt in the manufacturing and delays in the delivery of the Coronavac. On May 6th, the state of São Paulo expects to deliver another million doses of the vaccine to the federal government. There are no official estimates of exactly how many doses are lacking in Brazil to complete the immunization of those who have already been administered the first dose.
Source: DW