Both the European and US drug regulatory agencies have issued statements warning that there is currently no scientific evidence to support such a decision
The Spanish Minister of Health, Carolina Darias, declared during an interview on an Onda Cero programme (minute 19:59) on Friday 23 June that "everything seems to point" to the fact that the vaccine against covid-19 will have to be repeated every year, and that for this reason the European authorities are signing contracts with pharmaceutical companies to ensure the necessary vials for the years 2022 and 2023. Both the European and US drug regulatory agencies, meanwhile, have issued statements warning that there is currently no scientific evidence to support such a decision.
"Yes, without a doubt. Everything seems to point to yes. What will have to be determined is when."
Minister Darias responded to the journalist's questions: "Will we have to be vaccinated every year?" and "Will we have to have a third dose?", but despite the strength of her words, there are still no independent studies to ensure that a booster dose is currently necessary in the vaccinated population. For now, what is known after mass vaccination in most Western countries is that immunity lasts for five months after receiving the injection and, according to a paper published in Nature, it may be possible for the vaccine to be given in a booster dose, according to a paper published in Nature, it can even last for more than a year in those who have received an mRNA vaccine and have been previously infected with the virus.
The fear to the new variants
The justification of a third (and eventually, successive) dose relies on the possible emergence of new variables able to reduce the efficacy of vaccines. Currently, the most worrying is delta, detected in India, which is becoming dominant in countries such as the United Kingdom, where it has a 99% of prevalence. In Spain, for the moment, it is 43%. It has been observed that in the face of this variant, the efficacy of the vaccine with the full regimen slightly drops in Pfizer and Moderna.
These data are being used by pharmaceutical companies such as Pfizer as an argument in favour of the third dose, but the truth is that the Nature report also indicates that two doses do block infection, although the protection is somewhat lower.
Specifically, according to the latest data from the UK, Pfizer's vaccine protects against symptomatic infections in 88% of cases, while AstraZeneca's vaccine protects against symptomatic infections in 67% of cases. The report, published in The New England Journal of Medicine, adds that both are more than 90% effective in protecting against severe disease.
For the moment, the la European Medicines Agency (EMA) insists that it is "too early to confirm if and when a booster dose for COVID-19 vaccines will be needed, because there is not yet enough data from ongoing vaccination campaigns and studies to understand how long the protection of the vaccines will last, also considering the spread of variants".
However, in case booster doses are needed, they add, "the EMA and ECDC [the European Centre for Disease Prevention and Control] are already collaborating with each other and with national immunisation technical advisory groups (NITAGs), which are national experts who advise on vaccination programmes coordinated by the ECDC".
For its part, the Food and Drug Administration (FDA) has released a statement saying that "Americans who have been fully vaccinated do not need a booster vaccine at this time", although it acknowledges that it is working with the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH) "to consider if or when a booster might be needed".
In any case, they say they will continue to review "any new data as it becomes available and we will keep the public informed", and be "prepared for booster doses if and when science shows they are needed".
What about immunosuppressed patients?
Special mention should be made of those patients who suffer from a disease, illness or treatment that makes them immunosuppressed, that is, with a weak immune system. This group includes patients who have received transplants, those undergoing cancer chemotherapy, those suffering from autoimmune diseases, those with HIV and also those undergoing immunosuppressive treatments.
There is already scientific evidence that a third dose is recommended in these at-risk groups. Some reports are warning about the need for a third dose because it has been observed in transplant patients that they do not produce antibodies that fight the coronavirus even after two doses of messenger RNA (mRNA) vaccines. On the other hand, a third dose has been shown to reverse this situation, as explained in this study on the efficacy of Pfizer's formulation published in the The New England Journal of Medicine.
Other experts, such as Tedros Adhanom,president of the World Health Organisation (WHO), have denounced that the mere proposal of a third dose, especially when there are still countries such as Haiti or the Democratic Republic of Congo where the vaccination campaign has barely begun, is an unsupportive behaviour: as the WHO recalled a few weeks ago, "although more than 700 million vaccines have been administered worldwide, the richest countries have received more than 87% of these, and low-income countries have received only 0.2%. This is, in Adhanom's words, a "shocking imbalance in the global distribution of vaccines".
It has also been criticised that there is talk of a third dose when not even in Spain 70% of the population has been vaccinated, a number that the Spanish government has set as a target for achieving herd immunity, a percentage at which the number of infected people would theoretically start to fall (although this percentage is still under debate in the scientific community, with some even saying that it is impossible to achieve it).