Vaccines against covid-19 that are currently applied in some nations passed the tests of safety and effectiveness in clinical trials, creating immunity against the development of the disease at its three levels: mild, moderate or severe. However, the World Health Organization (WHO) warned that it is not yet clear whether these biologics fully protect people.
The expert of the international organization, Katherine O'Brien, explains that "they still do not know how long the immunity lasts" of the available vaccines or if they prevent those who have been immunized from being infected again with the disease, and can be a transmission factor for others persons.
That is why they are following up with the volunteers in order to find out if their immune response is prolonged. “(…) We will really have to wait for time to pass to see how long the effectiveness of these vaccines lasts. This is an important part of our understanding of what they do. Do they only protect against diseases or also against infection and transmission to another person, even if they do not have any symptoms? ”He said.
He adds that the effect of vaccines will evolve in line with new studies and research, even though these are only a complement to the fight against the pandemic, not the definitive solution. They are a way to prevent the long-term effects of COVID that "scientists are only beginning to understand," he said.
For her part, WHO chief scientist Soumiya Swaminathan said one thing is clear: Most of the clinical trials that have been reported achieve protection against serious illness that means hospitalization and death. There are eight vaccines in which human tests "have not been any fatal or serious cases, no matter which one they received," he says.
Swaminathan also points out that they have evidence of vaccinated people who have later become infected with the disease, but reflect a lower viral load and little chance of infecting others.
Another cause, that a vaccinated person can contract the virus again, is the percentage of effectiveness to which the drug responds. For example, a biological that reflects an efficacy of 95%, means that at least one in 20 people may not get protection, reports Johns Hopkins University.
Some of the vaccines that are already on the market are Pfizer / BioNTech, Sputnik V and AstraZeneca / Oxford. Additionally, a Johnson & Johnson drug is on the way for approval, as are Novavax and CureVac. Another nearly 70 are subject to clinical trials and about 181 are in the preclinical development phase, according to WHO data.
The scientific journal The Lancet attributed Sputnik-V to more than 91% effectiveness. The one created by the Pfizer-BioNtech laboratories has 95%; Moderna of 94,1% and the anticovid drug developed by the University of Oxford and AstraZeneca, 70%.
The Pan American Health Organization (PAHO) reported that it identified three variants in 14 Latin American countries. This raises concern and could aggravate cases. In this regard, Dr. O'Brien indicates that vaccines are not 100% effective, so it is necessary that protection measures be intensified, since the more the covid circulates, it is possible that new variants that resist vaccines may emerge.
"We must continue vaccination as quickly as possible and at the same time reduce transmission, since the more the virus is spread, the more likely it is to mutate and that there will be future problems of reduced effectiveness of the vaccines," he added.
Likewise, the WHO infectious disease epidemiologist, Maria Van Kerkhove, said that in South Africa a variant was identified that has greater transmissibility and with a better ability to find cells and infect them. Despite this, even with a greater contagion capacity, South Africa has managed to reduce infections with biosanitary measures.
The National Center for Vaccination and Diseases of the United States (CDC, for its acronym in English), indicates that none of the vaccines authorized in its territory contain the live covid virus, that is, that said biological compounds cannot make people immunized get sick. The symptoms they present are related to the protection conditions against the virus generated by the vaccine.
Now, during the period of creation of immunity and protection against the virus, which lasts at least two weeks, the vaccinated can become infected if they do not comply with health protocols. This is because the vaccine did not have enough time to generate protection in the body, and consequently the disease progresses. It may be the case that a person carrying the virus does not know it; the infection may continue to develop even after receiving the vaccine.
Types of immunity and vaccines
Keith Neal, emeritus professor of epidemiology at the University of Nottingham, in the United Kingdom, emphasizes that so far, the effectiveness of vaccines to combat the COVID-19 pandemic has been measured by their ability to prevent the development of symptoms, but there is still not enough data on whether they are able to avoid infection.
And, there are two main types of immunity with a vaccine: effective and sterilizing. The first is to prevent a pathogen from causing a serious disease, however, its immune pattern cannot prevent the pathogen from entering or making copies in the body, while the second can prevent infection and prevent asymptomatic cases. This last case rarely occurs.
Sputnik V is a type of viral vector vaccine that injects a different virus into the body that contains the genes for the covid spike protein; This generates a favorable immune response to impede the ability to spread and limit replication to some extent. In concrete terms, it uses a modified common cold virus to elicit a controlled response from the immune system.
Myths and rumors about vaccines
With the spread of Sars-Cov2, the cause of the covid-19 disease, not only myths and rumors have arisen about its origin but also with the treatments and vaccines to eradicate it. The WHO clarifies many of them:
- According to the multilateral organization, vaccines that have been evaluated and administered with its endorsement, do not cause infertility in people. There is no vaccine that causes infertility.
- There is no way that mRNA vaccines can convert or change the DNA of human cells.
- The compositions and chemicals they contain do not harm people who receive the vaccines. The existing ones so far are safe and have components that undergo rigorous tests.
- Each vaccine goes through a safety evaluation before it is used in people. In addition, the developers have constant quality supervision.
New mutations make the virus more infectious
A mutation in the Sars-CoV-2 spike protein found in the UK, South African and Brazilian variants can make the virus up to eight times more infectious than the original strain that appeared in China in 2019.
York, the New York Genome Center and the Mount Sinai Medical Center conducted a study on the D614G mutation, detected in all those variants that currently affect countries around the world.
"Confirming that the mutation leads to increased transmissibility may help explain, in part, why the virus has spread so rapidly over the past year," said Neville Sanjana, assistant professor of biology at New York University. He said the mutation has become "almost universally prevalent" among variants of the virus that are spread throughout the world.
The Mount Sinai researchers injected a virus with the D614G mutation into human lung, liver and colon cells and compared it to cells of the original strain detected in Wuhan at the beginning of the pandemic.
They found that the D614G variant increased the transmissibility of the virus up to eight times compared to the parent virus. The researchers also found that the mutation of the spike protein made the virus more resistant to being cleaved or divided by other proteins.