Two weeks after your second dose of COVID-19 vaccine, the protection of the vaccination will reach its highest level. At this point, you are fully vaccinated. If you are still infected with COVID-19 after this, you have already suffered a “breakthrough” infection. Broadly speaking, breakthrough infections are similar to routine COVID-19 infections in unvaccinated people—but there are some differences. If you have two jabs, please note the following.
According to the COVID symptom study, the five most common symptoms of breakthrough infections are headache, runny nose, sneezing, sore throat and loss of smell. Some of the symptoms are the same as those of people who have not been vaccinated. If you are not vaccinated, the three most common symptoms are headache, sore throat and runny nose.
However, the other two most common symptoms of unvaccinated patients are fever and persistent cough. Once you receive the jab, these two “classic” symptoms of COVID-19 will become less common. A study found that people with breakthrough infections are 58% less likely to have a fever compared with people who have not been vaccinated. On the contrary, COVID-19 after vaccination is described as feeling like a cold to many people.
If vaccinated people get COVID-19, they are also less likely to be hospitalized than unvaccinated people. They may also have fewer symptoms in the initial stages of the disease and are less likely to develop long-term COVID.
The vaccinated person’s milder disease may be due to vaccines. If they do not prevent the infection, it seems that the infected person will have fewer virus particles in their bodies. However, this has yet to be confirmed.
What increases the risk?
In the UK, studies have found that once fully vaccinated, 0.2% of the population-or one in 500 people-experience breakthrough infections. But not everyone faces the same risks. Four things seem to help you be protected by vaccination.
1. Types of vaccines
The first is the specific types of vaccines you receive and the relative risk reduction provided by each type. Relative risk reduction is a measure of the degree to which a person’s risk of COVID-19 is reduced by a vaccine compared to a person who has not been vaccinated.
Clinical trials have found that the Moderna vaccine reduces a person’s risk of symptomatic COVID-19 by 94%, while the Pfizer vaccine reduces this risk by 95%. Johnson & Johnson and AstraZeneca vaccines performed poorly, reducing this risk by approximately 66% and 70%, respectively (although the protection provided by the AstraZeneca vaccine seems to rise to 81 if you leave longer intervals between doses. %).
2. Time after vaccination
But these figures do not paint a complete picture. It is becoming more and more obvious that the length of time since vaccination is also important, which is one of the reasons why the debate about booster immunization has intensified.
Early research, still in the pre-printing stage (and therefore subject to review by other scientists), shows that the protective effects of Pfizer vaccines diminish within six months after vaccination. Another preprint from Israel also shows that this is indeed the case. It is too early to know what will happen to vaccine efficacy six months after double vaccination, but it may be further reduced.
Another important factor is the virus variant you are facing. The above-mentioned risk reduction is mainly calculated by testing a vaccine against the original form of the coronavirus.
However, when faced with the alpha variant, data from Public Health England showed that the protective effect of two doses of Pfizer vaccine was slightly lower, reducing the risk of COVID-19 symptoms by 93%. With regard to delta, the protection level further dropped to 88%. The AstraZeneca vaccine is also affected by this.
COVID symptom research supports all of these. Its data shows that within two to four weeks after receiving the second Pfizer injection, your chances of developing COVID-19 symptoms when facing delta are reduced by approximately 87%. After four to five months, this number dropped to 77%.
4. Your immune system
It is important to remember that the above figures refer to the average risk reduction for the entire population. Your own risk will depend on your own level of immunity and other personal-specific factors (such as your exposure to the virus, which may depend on your job).
Immune health usually decreases with age. Long-term medical conditions may also impair our response to vaccination. Therefore, the elderly or people with compromised immune systems may have a lower level of vaccine-induced protection against COVID-19, or may see their protective effects weaken more quickly.
It is also worth remembering that the most clinically vulnerable people were first vaccinated, probably eight months ago, which may increase their risk of experiencing breakthrough infections due to weakened protection.
Do you need to worry?
The vaccine will still greatly reduce your chance of contracting COVID-19. They also prevent hospitalization and death to a greater extent.
However, this has to do with seeing breakthrough infections and the fear that if vaccine protection does decline over time as suspected, they may increase. Therefore, the British government is planning to provide booster doses to the most vulnerable people and is also considering whether to provide booster doses more widely. Other countries, including France and Germany, have already planned to provide boosters to groups deemed to be at higher risk of contracting COVID-19.
But even if a booster is finally used, this should not be interpreted as a vaccine not working. At the same time, it is essential to promote vaccination to all those who meet the requirements but who have not yet been vaccinated.