The specialists and developers of vaccines against COVID-19 warn that They do not eliminate 100% the possibility of becoming infected with the SARS-CoV-2 coronavirus. What they do do is prevent the disease from developing seriously and ending up with mechanical ventilation and many other complications, or even death.
Vaccination, like contagion, immunizes the affected person to a certain degree, that, generally, You will not have symptoms or they will be mild in future reinfections. But that does not mean that the virus is eliminated or even that it can spread again. The key is in the activity of the immune system and in the proliferation capacity of the virus in these people. A trained immune system clears the virus before it can cause serious damage to the body.
It is also likely that those vaccinated have fewer symptoms during the initial stages of the disease and are less likely to develop long-term COVID. The reasons why the disease is milder in vaccinated people could be because the vaccines, if they do not block the infection, seem to lead to infected people having fewer virus particles on your body. However, this has yet to be confirmed.
“Vaccines are really very protective against serious disease, so eventhose who contract COVID-19 after two doses of the vaccine are much more likely to have a mild illness”, explained the doctor Bill Moss, pediatrician and professor of infectious disease epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore.
“The vaccine protects against severe forms of the disease. It does not prevent contagion 100%. That is why we say that the vaccine is one more element of protection against the virus and we must continue to take care of ourselves ”, said the infectologist consulted by this means Lautaro de Vedia, former president of the Argentine Society of Infectology.
What increases the risk of infection despite being vaccinated?
In the UK, a investigation found that 0.2% of the population, that is, one person in every 500, experiences a progressive or progressive infection once they are fully vaccinated. But not everyone is at the same risk. Four things seem to contribute to how well you are protected by vaccination.
1. Type of vaccine
The first is the specific type of vaccine the person received and the relative risk reduction provided by each type. Relative risk reduction is a measure of how much a vaccine reduces the risk of someone developing COVID-19 compared to someone who was not vaccinated.
Clinical trials found that the vaccine Modern reduced a person’s risk of developing symptomatic COVID-19 in a 94% while the vaccine Pfizer reduced this risk by 95% . The Johnson & Johnson and AstraZeneca vaccines performed worse, reducing this risk by approximately one 66% and 70% respectively (although the protection offered by the vaccine AstraZeneca it seemed increase to 81% if a longer interval between doses was left).
2. Time elapsed since vaccination
But these figures don’t paint the whole picture. It is increasingly evident that the time elapsed since vaccination is also important And it’s one of the reasons the booster vaccine debate is growing in intensity.
The first investigations, still in prepress (and therefore have yet to be reviewed by other scientists), suggest that the protection of the Pfizer vaccine decreases during the six months after vaccination. Other pre-established Israel also suggests that this is the case. It is too early to know what happens to the efficacy of the vaccine beyond six months in the double vaccinated, but it is likely to be further reduced.
3. Variants of the virus
Another important factor is the variant of the virus you are dealing with. The risk reductions mentioned above were largely calculated by testing vaccines against the original form of the coronavirus. But when faced with the alpha variant, the data from Public Health England suggest that two doses of the Pfizer vaccine are slightly less protective, reducing the risk of contracting COVID-19 symptoms by 93%. Against delta, the level of protection drops even further, to 88%. The AstraZeneca vaccine is also affected in this way. The COVID Symptom Study supports all of this. Their data suggest that within two to four weeks after receiving your second injection from Pfizer, you are about 87% less likely to have COVID-19 symptoms when faced with delta. After four to five months, that number drops to 77%.
4. The immune system
It is important to remember that the above figures refer to the reduction average risk in a population. its Own risk will depend on your own immunity levels and other factors specific to the person (such as how exposed you are to the virus, which could be determined by your job).
Immune fitness generally declines with age. Long-term medical conditions can also affect our response to vaccination . Therefore, older people or people with compromised immune systems may have lower levels of vaccine-induced protection against COVID-19, or they may see their protection decline more rapidly. It is also worth remembering that the most clinically vulnerable received their vaccinations first, possibly more than eight months ago, which may increase the risk of experiencing a breakthrough infection due to decreased protection.
Vaccines can cause two main types of immunity. On the one hand, the “Effective immunity”, which can prevent a pathogen from causing serious illness, but cannot prevent it from entering the body or making more copies of itself. And on the other, the “Sterilizing immunity”, that it can prevent infection and even prevent asymptomatic cases. Ideally, a vaccine can produce sterilizing immunity.
For Moss, once the population has been fully vaccinated, meaning they have received both doses of the vaccine and waited two weeks after the second dose, you should take the same precautions, such as wearing a chinstrap and social distancing in public. “There is nothing different that people should be doing now that we start getting vaccinated,” said the specialist.
“Vaccines matter more when a significant part of the population receives them,” he stressed. Andrew Heinrich, professor at Yale School of Public Health in New Haven, Connecticut. “It is a somewhat logarithmic scale and (as more people get vaccinated) the benefits start to increase enormously. The best we can do to make vaccines effective is to vaccinate as many people as they are eligible ”, concluded the expert.