Do we know if it is safe, what side effects it can cause and, if it is effective, how it will protect us?
Lets start by the beginning. The ChAdOx1 nCoV-19 vaccine, developed by the University of Oxford, consists of viruses that affect chimpanzees and have been modified to resemble SARS-CoV-2 (they have a component of their envelope, the S protein). Thus, when this vaccine is inoculated into our body, the immune system reacts as if it were the coronavirus, only without the slightest risk of developing the disease.
The tactic is not new: many of the vaccines we receive as children work the same way. The result is that the body prepares itself so that, if we do contract the infection, it does not produce the disease. Or in any case, if there is any effect, let it be as slight as possible. To put it another way, we “introduce” you to SARS-CoV-2 so that it is not a complete stranger to you.
With vaccination we not only manage to avoid the disease, but we also contribute together so that the virus is not transmitted. We protect ourselves and we protect others. A clear example of how the strategy works can be found in the recent eradication of polio in Africa.
Safety and efficacy in experimental animals
Before starting human trials, the preclinical phase mandatorily includes testing the vaccine in non-human primates, usually macaque monkeys. They are the best model because their immune system is very similar to ours and they suffer from the infection in a similar way . In addition, once vaccinated they are deliberately infected to analyze if the vaccine works.
The Oxford researchers found antibodies against SARS-CoV-2 two weeks after inoculating the animals with the vaccine and were not found in those that had not received it, used as controls. The animals that had received double doses had more antibodies and did not observe adverse effects in either of the two groups. They also detected an increase in interferon as a sign of a good cellular immune response (T cells). These effects are those that are intended to achieve in a vaccine.
However, after infecting them with SARS-CoV-2, all the animals had viruses in their respiratory tract, although none of them suffered from pneumonia (according to the analysis of their lungs), or diseases in other organs.
The conclusion was that the vaccine appears safe, without adverse effects, but it did not prevent the proliferation of the virus in the animals (they became infected and could transmit it), although it significantly reduced the disease.
But does it work in humans?
The results of the first human studies (phases I and II) have recently been published. In the trials, 543 healthy people (18 to 55 years old) were injected with the SARS-CoV-2 vaccine, and 534 people were injected with a different vaccine (meningococcus, which causes another disease). Why meningococcus? Because comparing results with something known and of proven efficacy provides very valuable information to test new treatments.
Next, the level of antibodies in the blood of the vaccinated individuals was analyzed using serological tests (ELISA) 28 days after vaccination. What was detected was a clear increase in antibodies from the level before vaccination. When injecting a second dose, the level of antibodies continued to rise, and it was also found that they reacted against the SARS-CoV-2 virus (neutralized it). It was also observed that at 14 days memory lymphocytes (mature T cells) increased, as in monkeys.
And what about your security?
To analyze the reactions to the vaccine, part of the individuals was administered paracetamol before vaccination. The observed symptoms described in the figure are typical of most other vaccines that have been shown to be safe for a multitude of diseases.
The maximum intensity of symptoms was manifested one day after vaccination. And they disappeared completely before 7 days. Although some reactions showed severe characteristics, in no case was hospitalization necessary. As for the second dose, it also produced some effect, but always milder.
The exhaustive follow-up of the health of the participants will last for one year. It’s one of the reasons it takes time to get a vaccine or drug definitively approved: to check the long-term safety and efficacy of the vaccine.
But there is still …
The researchers note that more tests are needed with more people with different characteristics of age (children and the elderly), health, etc. before you are sure that the vaccine is effective. In fact, the next phase is already being prepared, which includes the vaccination of thousands of individuals in Brazil, South Africa and the United Kingdom.
Why in those countries? Because vaccination in regions where it is currently easier to acquire the disease will allow obtaining the necessary data to complete the experimentation. The results and conclusions of these studies will determine whether the vaccine will be used for the prophylaxis of COVID-19.
Transparency and truthfulness
What seems indisputable is that publication in scientific journals on how drugs and vaccines are being developed is an essential requirement. Mainly because it implies that these results are meticulously reviewed by other researchers to detect any failure or omission, granting the level of veracity that characterizes the advancement of science.
The current health crisis is allowing everyone to know the ins and outs of each of the new vaccine investigations to be able to acquire a criterion about them. Society has suddenly become interested in scientific topics that it did not understand a few months ago, such as the functioning of the immune system.
It should be noted that this is positive and exceptional. Moreover, it is a very important advance to bring scientific research closer to the whole of society, which is to whom it is addressed. In matters as important as health, and specifically vaccines, you must know how they work and how safe they are. One of the responsibilities of scientists is that this information reaches the whole of society, so that the irrational fear of vaccines does not gain ground.
María Mercedes Jiménez Sarmiento, CSIC Scientist. Systems Biochemistry of the bacterial division. Scientific communicator, Margarita Salas Biological Research Center (CIB – CSIC); Matilde Cañelles López, Scientific Researcher, Center for Human and Social Sciences (CCHS – CSIC) and Nuria Eugenia Campillo, Senior Scientist. Medicinal Chemistry, Margarita Salas Biological Research Center (CIB – CSIC)
This article was originally published on The Conversation. Read the original.
