Some Covid vaccines are less effective against variants of the virus; others remained neutral and some still have no results released. Understand how is the ‘fight’ of immunizers that we have today against the changes that Sars-CoV-2 has been undergoing. Have the vaccines we have today been shown to be effective against the coronavirus mutations and variants detected so far? The short answer is: as far as is known, in general, yes.
The longest answer is, some vaccines have reduced their effectiveness against some of these changes in Sars-CoV-2, but have still been able to induce a response from our body’s defense system against them. Other immunizers have not yet reported results against these mutations and variants.
Will vaccines continue to be effective in the future against these changes? Science doesn’t know yet, but the general warning, from scientists around the world, is: we need to speed up the application of vaccines and increase the number of doses available. Rapid vaccination, with the vaccines we already have, becomes even more fundamental “, completes the scientist. Also, researchers agree on a second point: we must have several vaccines available – both in Brazil and in the world -, of various technologies, precisely to combat the new variants and expand vaccination coverage.
In this report, you will see how the “fight” of vaccines we have today is with the most worrying variants of Sars-CoV-2, the coronavirus that causes Covid-19. A variant is a “version” of the coronavirus, in other words. When a mutation (a change) begins to appear many times in the virus, in genetic sequencing, it means that it has “fixed”. This configures a variant about the previous “version” of the virus, the ancestor. In the case of P.1, at least three other states besides Amazonas have already registered cases: Para, Bahia, and São Paulo. It has also been detected in at least 13 countries in addition to Brazil, according to international monitoring of strains of the virus that includes researchers from Oxford and Cambridge. The list of countries includes Japan, the United States, and Germany.
The British and South African variants have also been found in Brazil.
In the infographics below, you can see, by technology (platform), the main vaccines that are being applied in the world today or that are in the last phase of human testing (phase 3). Some of them have already released their preliminary results and four – Moderna, Oxford, Pfizer, and Sputnik V – have already had these data published in magazines. When this happens, it is because they have been evaluated and validated by other researchers.
Inactivated vaccines (such as CoronaVac, Sinopharm’s, and Bharat biotechs) may have advantages against variants because the body starts to “recognize” all parts of the virus, and not just protein S. The other types of vaccine have bet on protein S as the target of the immune response.
But this possible advantage is still theoretical and needs to be studied better, says Carlos Zárate-Bladés, from UFSC. Viral vector vaccines (like Sputnik V, Johnson’s, and Oxford’s) and RNA vaccines (like Moderna’s and Pfizer’s) may not be effective against the variants because the piece of genetic material that is used gives instructions for the body to build protein S, which the virus uses to infect cells. If the virus mutates and that protein changes, the vaccine may no longer work.
On the other hand, these two types of vaccines have been shown to have some capacity, albeit sometimes diminished, to neutralize coronavirus variants. (See details below).
For Zarate-Blades, one of the hypotheses for these vaccines to be working so far is that the mutations that the coronavirus has had were not large or large enough to alter the epitope – the portion of the virus that is recognized by neutralizing antibodies. When we are vaccinated, we make neutralizing antibodies against coronavirus S protein, and then they block the virus when it enters. So, even if these variants of the new virus have changed, most likely these changes did not substantially interrupt the recognition by antibodies of the immune system “, explains the scientist.
Protein subunit vaccines (Novavax and Anhui Zhifei) may face problems similar to those of RNA and viral vector. If the protein the virus uses to infect cells is no longer the one in the vaccine, the body won’t recognize it as an invader, either.
“You need to find out which combination of antigens [pieces of the virus] will provide the necessary immune response,” explains Rafael Polidoro, an immunology researcher at Indiana University in the United States. Subunit vaccines have one more detail: the proteins they use are denatured. In the real virus, they are not, explains Polidoro. This means that the proteins that the body “sees” in the vaccine are not the same as those that the virus has.
So, the body makes antibodies against a protein that is the one, but not exactly that “, says the scientist. The variant is just that: a variant alters one or more amino acids in the [genetic] sequence and the protein changes so much in conformation that its denatured [vaccine] protein is very distant from the new one [of the virus]”, adds Polidoro.
“Imagine that [the protein] is like bending a knee. Any physical variation – instead of turning a knee, it looks like an elbow, a little more acute – it’s gone, [the vaccine] doesn’t work anymore. This is an of the problems of protein vaccines “, he says.
The Novavax vaccine, which uses protein subunits, has had its effectiveness greatly reduced against the South African variant. Anhui Zhifei’s, on the other hand, managed to maintain the neutralization of the virus (see details below). One of the possibilities for this variation, even in vaccines with the same platform, is that Novavax used insect cells (moths) to express the coronavirus protein, says Carlos Zarate-Blades. In the case of Novavax, this protein is produced in insect cells – which are excellent for making proteins, but still not the same as human cells. These small differences in the final product can be very important when stimulating the immune system. “, explains the scientist.
On Friday (5), Oxford researchers announced, in a preliminary analysis, that their vaccine was effective against the British variant of the coronavirus. On the other hand, another initial study pointed out that the vaccine may have reduced efficacy against the South African variant. The country has suspended the application of the immunizer. Pfizer and Moderna announced that their vaccines were able to neutralize variants of the coronavirus in the laboratory – including the British (B.1.1.7) and the South African (B.1351 or 501Y.V2). However, both had a fall in the neutralization capacity against the South Africa variant (because of the E484K mutation, which is also in the Brazilian variants).
Both laboratories said they would test new formulas to ensure protection against coronavirus mutations. The Sinopharm (BBIBP-CorV) and Anhui Zhifei (ZF2001) vaccines managed to neutralize the South African variant without a large drop in neutralizing antibodies. The study is still in a previous version (pre-print), but the researchers pointed out, in the conclusion, that the data suggest that whole virus vaccines – the inactivated ones – or those that target the RBD region, which is the virus uses to bind to cells, they must maintain their protective effect against the South African variant. Johnson announced that its vaccine was 57% effective against the South African variant, one of the countries where it was tested.
The rate was lower than that found for other variants of the virus, but above the minimum recommended by the World Health Organization (WHO), which is 50%.
Novavax reported that its vaccine had much lower efficacy for the South African variant compared to others of the coronavirus. While UK data pointed to 89.3% effectiveness, tests in South Africa found 49.4% effective. Of the 27 cases of Covid-19 found there during the tests, 25 had the local variant of the coronavirus. The vaccines developed by Sinovac (CoronaVac) and the Gamaleya Institute (Sputnik V) have not yet announced their results against new variants. No vaccine developer has so far disclosed how they have fought specifically against the virus variant found in Amazonas that most worries scientists.