Article by SalvadorPeiró(@VoroPeiro), researcher in the Health Services and PharmacoepidemiologyResearch Area. Foundation for the Promotion of Health and Biomedical Research ofthe Valencian Region - FISABIO, Valencia.

‍

‍Vaccination, which has not yet reached 70% of the immunised population, has already changed the course of the pandemic in Spain. The last time we had such a high incidence of Covid-19 cases as in the last few days (around 25,000 cases/day, with a cumulative incidence of close to 700 new cases per 100,000 inhabitants in the last 14 days) was at the beginning of February this year.

By then we hadbegun the decline of the third wave: 2,000 people were hospitalised, 200 were admitted to the ICU every day and more than 500 died every day.

Now hospitalisations are around 400 per day, five times less than in February this year; daily ICU admissions are less than thirty, seven times less than in February; anddaily mortality is of around a dozen people. Twelve times as many as we would like, but forty times less than in February.

The difference between one moment and another lies in the vaccines and a vaccination strategy that, although sometimes controversial, has prioritised the most vulnerable element: the elderly and some specific groups of people.Although the percentage of Spaniards with the full vaccination schedule is of around 54% of the population, 85% of those over 40 years of age and practically all of those over 70 years of age are vaccinated.

All the autonomous communities have made an unprecedented effort to administer vaccines. The Autonomous Communities have administered, on average, more than 95% of the doses received and Spain has surpassed the United States and the United Kingdom (countries with the greatest and earliest access to vaccines) in terms of the percentage of the population with a complete vaccination schedule. Moreover, the country shows a higher vaccination speed than the EU average, despite having similar access to vaccines.

Predictably,vaccination has already changed the face (and reverse) of the pandemic long before reaching the magic figure of 70% of the population fully vaccinated; it has already saved thousands of lives in our country. But, as was also predictable, and will remain so even after reaching 70% vaccination, the pandemic is not yet over.

The current ‘puzzle’: vaccines,unvaccinated persons, high transmission, Delta variant

The pandemic isnot only continuing, it is growing. The proportion of severe cases islower, much lower. The most at-risk populations are vaccinated and the unvaccinated, because of their age, have a lower risk of developing the most severe forms of covid-19. But there are many of them. And although we now have a trickle of severe cases rather than a torrent, many leaks over time also fill- and overflow - the wells. This situation forces us to consider the following issues.

The full vaccination schedule remains remarkably effective against symptomatic Covid-19, hospitalisation, and death with all virus variants, including Delta. But perhaps –as has been pointed out in Israel– it does not reduce transmission as much. In contrast, incomplete vaccination schedules offer less protection against symptomatic disease with the Delta variant, although they maintain their effectiveness against the risk of hospitalisation.

On the other hand, this immunity appears to be very long-lasting, even in frail persons, and reinfections and symptomatic cases after vaccination appear to be very rare.

The Pfizer/BioNTech, Moderna and Oxford/AstraZeneca vaccines have clear laboratory and clinical evidence demonstrating their effectiveness against the Delta variant. Janssen's single-dose vaccine has less information: only laboratory information and controversial at that.

Its limited usein the countries that are providing the most evidence with real-life data, such as the UK, Israel, and the US, limits our information and possible strategies, such as whether booster doses will be necessary. It is important to obtain this information in countries where we have used this vaccine.

‍

"Vaccinate. Get vaccinated. And buy time for the vaccination to be effective"

The combinationof these data reinforces the need for contact restriction measures while vaccinating the younger population groups: they will need five to six weeks following vaccine administration to achieve optimal immunity.

This is because the high transmissibility of the Delta variant also affects virus transmission among those vaccinated. Although most of them will not develop severe disease, they can transmit the infection. This means carefully designing the restrictions to which they should be subjected, for example in case of close contact.  

In this context,if those vaccinated can transmit the virus, herd immunity does not protect the unvaccinated as effectively. Anyone who chooses not to be vaccinated on the assumption that the vaccinated will protect them is likely tobecome infected and could develop severe illness.

The current pandemic situation in our country is reminiscent of those horror movie endings in which, just when you think it's all over, the last scare arrives. Even if this is summer, no matter how few deaths there are, here and now, we must avoidthe feeling that everything is over.

Vaccinate. Get vaccinated. And buy time for the vaccination to be effective. And that means, fundamentally, continuing to keep contact with non-cohabitants to a minimum.

What really matters: that as many people as possible attain immunity through vaccination, without having been immunised through the much riskier wild route.

‍

This article is also available in Spanish.