Coronavirus health news
The effectiveness of the different vaccines against SARS-CoV-2 continues to raise concerns, as happened last weekend in Chile, where a controversy arose over the effectiveness of the Sinovac vaccine, with which the government is inoculating the majority of its population. Given the doubts extended to other Latin American countries, in general regarding all vaccines, it is important to understand the characteristics and differences between them.
In this regard, the German virologist Felix Drexler, from the Berlin Charité, explains to us by groups the types of authorized vaccines that exist so far, how effective they are and against what types of variant they could protect. And also those to come:
Messenger RNA or mRNA
The coronavirus vaccines developed under this technology are Pfizer / BioNTech and Moderna. These types of vaccines, Dr. Drexler recalls, are the newest because of the way they generate antibodies. Something that has never been successfully achieved before.
This technique consists of injecting RNA fragments with instructions that produce antibodies to the protein S (spike) of SARS-CoV-2. By creating this protein, the body learns to defend itself against it. So if a person becomes infected with the real virus, they already have antibodies capable of fighting it. “Our body produces proteins, starting with the nucleic acid DNA, which is our genome, through an intermediate called messenger RNA. It is called a messenger because the message it carries is the protein that must be produced in our cells, the S protein ”, explains Dr. Drexler.
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“With it, a very great advance in biotechnology has been achieved. And it is capable of forever changing the way we vaccinate, also against other diseases such as cancer. Furthermore, taking into account the mutations, this technology is much easier to change than that of the other types of vaccines ”, assures the German virologist.
Pfizer / BioNTech's efficiency is 95% and Moderna's 94.1%. Two doses of this vaccine are required 21-28 days apart. For the storage of the first one, deep freezing is necessary, between -70 and -80 degrees Celsius. Moderna's needs to be refrigerated to -20 degrees Celsius.
Adenovirus or adenoviral vector
The method that has been used for the AstraZeneca, Johnson & Johnson and Sputnik V vaccines uses a fragment of the coronavirus genetic code that is mixed with a harmless virus, called an “adenovirus vector”, which serves to transport this genetic material to body. Adenoviruses carry protein S (spike), which causes antibodies to be produced.
“They are adenoviruses other than chimpanzees, into which genetic material was introduced. When introduced into humans, it achieves a response without causing disease. Adenoviruses are vector, that's why we call them vectorized vaccines. While AstraZeneca and Johnson & Johnson use the same vector in the delivery of their doses, the Sputnik V vaccine uses two different adenoviruses in the first and second doses, ”says Dr. Drexler.
AstraZeneca studies have shown an efficacy of 82.4% and Johnson & Johnson 83.5%. However, in some countries vaccination with both has been stopped because in some isolated cases they cause thrombosis or blood clots. In this regard, Dr. Drexler comments that what causes these risks is still not very well understood: “It seems that it may be due to the only vector used. But, in general, we must remember that everything is a very transparent process, cases are being investigated and recommendations are being adapted, remembering that every vaccine has a cost-benefit relationship ”.
Adenovirus vaccines can be stored in normal refrigeration between 2 to 8 degrees Celsius. Two doses are required for AstraZeneca and only one for Johnson & Johnson. However, that could vary, as it depends on what each manufacturer has.
Inactivated virus or attenuated virus
Chinese pharmaceutical companies are the ones that have used this method for the Sinopharm and Sinovac vaccines, which have been purchased mostly in Latin America. The technique, which is a pioneer in the development of vaccines, uses attenuated or killed microorganisms of the virus to generate immunity.
“A virus is processed in cell culture until it has many viruses and it is activated by a toxic substance, which destroys the virus, and the virus proteins that have been cultured immunize the person. It is a very classic way of producing a vaccine against a virus. We are seeing that now it may have a slightly reduced efficacy, according to information from China, but that is not yet certain ”, says the virologist from the Berlin Charité.
The efficacy of the Sinopharm vaccine would be 79.3% and that of Sinovac would be between 50.38% to 100%. Of both, two doses are generally required. For its storage it would also need a normal refrigeration of between 2 to 8 degrees Celsius.
Regarding the duration of immunity that the vaccines would give, there are only, so far, some studies that indicate that those of Pfizer / BioNTech and Moderna would protect around six months. On the efficacy of vaccines, in general, against the new variants, the German virologist does not dare to give a prognosis. “The studies are underway. You have to remember that today's vaccines were developed based on the original coronavirus and not on mutations, ”says Dr. Drexler.
Vaccines on the way
Given the arrival of new vaccines, the expert is very optimistic, especially with Novavax. “This will also be very important in the fight against COVID-19 in Latin America, because it is more heat stable. There is also the German Curevac, which is messenger RNA, but is a little behind in its tests. Furthermore, without getting into politics, the development of the Cuban vaccine is a very positive sign. They have a very important biomedical tradition in the region ”, emphasizes Dr. Drexler.
Following what was said by the World Health Organization (WHO), Dr. Drexler recalls the importance of getting vaccinated with any of the vaccines that are available in each country: “Getting vaccinated does not mean that we are not going to get infected, but we do it will avoid an aggravation of the disease, of that there is no doubt by the studies. We must not be afraid, we must get vaccinated as soon as possible ”. (I)
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