The corona vaccine candidate from the US pharmaceutical company Pfizer and its partner Biontech provides new hope in the fight against the pandemic. On Monday, the drug companies announced that their vaccine was more than 90 percent effective, based on 94 cases of the disease seen in their Phase III clinical trial. Emergency approval from the US Medicines Agency is now expected within a few weeks.
However, Pfizer’s vaccine requires two doses to achieve this high level of effectiveness. The two doses are given three weeks apart. In July, the US company reported that its researchers observed the highest levels of virus-neutralizing antibodies in the participants a week after the second dose.
Other corona vaccine candidates that are still in clinical trials also require double vaccinations: Participants in the Moderna clinical trial will receive two doses four weeks apart and in the ongoing AstraZeneca trial, the results will be obtained with both a single vaccine dose and tested with two doses one month apart.
However, having a two-dose vaccine poses supply chain challenges. There is also the possibility that not everyone will come to the appointment for the important second dose of vaccine.
Double dose – double problems
A double dose vaccine also requires twice the number of syringes, refrigeration facilities and clinic visits at a time when those resources are already limited.
As things stand, the Pfizer vaccine must be shipped and stored at minus 70 degrees Celsius. This poses an enormous challenge to distribution in developing countries, especially in places where there is already a lack of electricity or good infrastructure of health facilities.
In addition, it could be difficult to get 100 percent of vaccine recipients to follow up. “The more complicated the schedule, the harder it is to get people to come back,” Walt Orenstein, vaccine doctor and former director of the US National Immunization Program, previously told NewsABC.net.
For example, research shows that less than a third of young women who received the first dose of a cervical cancer vaccine returned for the remaining two doses to complete the vaccination.
Will regular vaccinations be necessary?
Scientists haven’t been able to study the coronavirus long enough to see how long immunity lasts. But there are indications that people could become infected again. Research has found that coronavirus antibodies resolve over a period of weeks or months, which could mean that our immunity – whether generated in response to an infection or a vaccine – can be similarly transient.
However, our immune system has more than just antibodies to defend itself, so many questions about immunity to the virus remain unanswered. “If the immunity turns out to be volatile, we need a vaccination plan plus booster or regular vaccination,” disease ecologist Marm Kilpatrick told NewsABC.net. So it is not unlikely that people will become susceptible to infection again a while after vaccination.
That wouldn’t be unusual. “That happens with a lot of vaccines,” says Florian Krammer, vaccine doctor at the Icahn School of Medicine. “It’s not a problem. You can be vaccinated again. “
This is what so-called booster shots are for. For example, the tetanus vaccination requires a booster every ten years. The question is how often will this be required with corona vaccines?
Experts cannot determine whether boosters will become part of the vaccination until the vaccines are introduced. Pfizer has announced that the majority of the cans – up to 1.3 billion – will be ready in 2021.
“As soon as we see that vaccination failures are increasing, we can consider booster doses. However, we do not know at this point whether this will be necessary, ”Orenstein said.
7 open questions about Pfizers and Biontech’s corona vaccine
This article was translated from English by Klemens Handke. You can find the original here.