Will Spain be able to vaccinate 70% of the adult population by the end of summer?

Spain has administered two doses of the Covid-19 vaccine to 2.6% of the population. Although the pace of the vaccination drive picked up in the last week of February, the rollout has been more or less steady over the month: every day, 0.17% of the population are injected with one dose, which equates to around 500,000 people per week. At this rate, the European Union’s target of vaccinating 70% of the adult population before the summer – amounting to 58% of Spain’s total population – will not be met. As the graph below shows, if the current speed is maintained, barely 20% of the total population will have received two doses by September.

Spain’s regions – which are in charge of the vaccination campaign as well as handling the response to the pandemic in their territories – have been prioritizing the second dose of the Covid-19 vaccine, in accordance with the Health Ministry’s protocol. The three vaccines that have so far been approved by the EU – from Moderna, Pfizer and Oxford-AstraZeneca – all require two doses, separated by a specified interval. As a result of this strategy, the first dose is administered for around three weeks, then alternates with the second dose for another three-week period. The solid lines on the graph represent the evolution so far: about 3% of Spaniards have received both doses and another 1% have received the first dose and are waiting for the second. The dashed lines show how the numbers of people vaccinated will evolve if the current rate is maintained.

To reach the 70% target, weekly vaccinations in Spain will have to increase fourfold. The central government is confident this will happen. The Health Ministry announced that 6.5 million doses of the AstraZeneca, Moderna and Pfizer vaccine would arrive in Spain by the end of March. And there million-euro contracts for the new vaccine by Janssen – which only requires one dose – and the vaccine by CureVac for the coming months. However, for Spain to be able to quadruple the number of weekly doses administered, two conditions must be met: the vaccines must arrive on time – there have been delays in the past – and it must have the capacity to administer them.

In general, Spain has been administering vaccines at the rate at which they have been arriving. As of February 25, Spain had administered 87% of doses received, one of the highest percentages in the European Union, according to data from the European Center for Disease Prevention and Control (ECDC), which has pointed to limited supply as the biggest challenge to the EU rollout. Spain has not yet had a problem administering the received doses, but it could start to become one. While the first phase of Spain’s vaccination campaign targeted staff and residents of care homes, frontline health workers and adults in need of daily care who were not in residences – who can be easily located – the next stage includes members of the general population, such as essential workers, which may present difficulties. “Vaccinating professional groups is more complex,” explains Jaime Jesús Pérez, a doctor from the Vaccinology Association. “You have to have at least two weeks just to organize the information on who gets vaccinated and who doesn’t.”

The country with the fastest vaccination campaign is Israel, where 37% of the population have received two doses and 53% have received the first. This has been achieved by vaccinating more than 200,000 people a day – the equivalent of 2% of the population. In Spain, this rate is 0.17%, nearly one-third of the speed in the United States (0.45%) and the United Kingdom (0.5%)

Best-case scenarios

The speed of the vaccination drive in Spain is likely to accelerate. In fact, 30% more doses were administered in the last week of February than the previous week. As well as receiving more vaccines, the country is also learning how to optimize the process. As Jesús Pérez points out: “We are seeing the usefulness of mass vaccination points, such as sports centers, which are going to be key when there are more vaccines. A lot of people can arrive at the same time and wait while maintaining a safe distance, something that is impossible at a health center.”

The question is whether the rate will increase enough to reach the goal of immunizing 70% of adults by summer. Here’s how vaccination would progress in three possible scenarios.

Four times the number of doses. Last week, Spanish Prime Minister Pedro Sánchez told the lower house of parliament, the Congress of Deputies, that the number of vaccines arriving would increase fourfold in the second quarter of the year. The repercussions of this are evident in the graph below, which shows how the number of people vaccinated would progress if, as of April 19, the number of doses administered is multiplied by four. With this acceleration, by the beginning of September, around 58% of people would be vaccinated, surpassing the threshold of 70% of adults.

At the US rate. Another optimistic reference based on the actual experience of other countries is to assume that the rate of vaccination in Spain can match the current rate in the US, where 0.45% of the population receives one dose a day. It would not, however, be enough to reach the EU’s goal: 50% of the entire population would be vaccinated by the end of the summer, accounting for 60% of adults.

And if just the first dose is administered?

The above scenarios are all simulations based on the same strategy, which is the one followed in Spain: second doses are always prioritized, so that there are three weeks in which a group of people receive their first dose and then another three weeks in which the same people receive a second. In this way, there are periods of three weeks where only one dose is given and another three-week period where the second dose is given.

Spain’s regions have so far followed this strategy, with the idea that it guarantees maximum protection for the groups being vaccinated. As can be seen in the graph below, there are three weeks when only the line representing first doses goes up; then it stops and the line for the second dose starts to rise.

The model is not perfect, because there are exceptions and because regions can vaccinate at different speeds. And it will most likely become less clear as time goes by. For the moment, it is confirmation that Spain, like most of Europe, is following a vaccination protocol that seeks to maximize the number of people who have received both doses.

This is how the doses are alternated in most European countries

Vaccines

received

Administered

1ª

Every week two groups of people are vaccinated.

2ª

3ª

4ª

From the fourth week, the second dose is administered.

5ª

6ª

7ª

By the end of the sixth week: six groups have received the two doses

8ª

9ª

10ª

11ª

12ª

13ª

By the end of the 12th week: 12 groups have received thetwo doses

This is how the administration of the doses is alternated in most European countries

Vaccines

received

Administered

1ª

Every week two groups of people are vaccinated.

2ª

3ª

4ª

From the fourth week, the second doseis administered.

5ª

6ª

7ª

By the end of the sixth week:six groups have received the two doses

8ª

9ª

10ª

11ª

12ª

13ª

By the end of the 12th week: 12 groups have received the two doses

This is how the doses are alternated in most European countries

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Vaccines received

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Administered

Every week two groupsof people are vaccinated.

From the fourth week, the second dose is administered.

By the end of the sixth week:

six groups have received the two doses

By the end of the 12th week:

12 groups have received the two doses

This is how the doses are alternated in most European countries

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Vaccines received

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Administered

Every week two groupsof people are vaccinated.

From the fourth week, the second dose is administered.

At the end of the sixth week:

six groups have received the two doses

At the end of the 12th week:

24 groups have receivedthe two doses

But this is not the only viable strategy. In the UK, the authorities opted from the outset to administer as many first doses as possible and to postpone the second doses – from Pfizer and AstraZeneca – by up to 12 weeks. The aim is to reduce the spread of the virus as soon as possible by immunizing as many people as possible: in the first three months the pace is very fast and the number of people who have at least partial protection doubles.

The UK strategy: administer as many first doses as possible over 12 weeks

Vaccines

received

Administered

1ª

Every week two groups of people are vaccinated.

2ª

3ª

4ª

5ª

At the end of the sixth week: six groups have received the first dose

6ª

7ª

8ª

9ª

At the end of the 12th week: 12 groups have received the first dose

10ª

11ª

12ª

13ª

From the inyectar segundas dosis a personas ya vacundadas.

The UK strategy: administer as many first doses as possible over 12 weeks

Vaccines

received

Vaccinations

1ª

Every week two groups of people are vaccinated.

2ª

3ª

4ª

5ª

At the end of the sixth week: 12 groupshave received the first dose

6ª

7ª

8ª

9ª

10ª

Al finalizar la 12ª semana: 12 grupos con primeras dosis inyectadas

11ª

12ª

13ª

A partir de la 13ª semana se empiezan a inyectar segundas dosis a personas ya vacundadas.

The UK strategy: administer as many first doses as possible over 12 weeks.

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Vaccines received

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Administered

Every week two groups of people are vaccinated.

At the end of the sixth week:

12 groups have received the first dose

At the end of the 12th week:

24 groups have received the second dose

The UK strategy: administer as many first doses as possible over 12 weeks

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Vaccines received

1ª

2ª

3ª

4ª

5ª

6ª

7ª

8ª

9ª

10ª

11ª

12ª

13ª

Week

Vaccinations

Every week two groups of people are vaccinated.

At the end of the sixth week:

12 groups have received the first dose

At the end of the 12th week:

24 groups have received the first dose

The following graph shows what the situation in Spain would be like if the country had followed a strategy similar to the one in the UK. At the current speed of the Spanish vaccination drive, 5% of the population would have received at least one dose and almost 20% would have received one by the end of May, when second doses would begin to be administered. By the end of the summer, 25% of the population would have received one dose and about 20% would have been given two doses.

Most countries rejected the UK strategy because the outcome was less assured – the results of the Pfizer or Moderna trials had focused on testing efficacy of two doses separated by three to four weeks. But studies using data from Israel and the UK are finding that the first dose already offers considerable protection against Covid-19 and the risk of hospitalization. It may also prevent up to 50% of transmission one month after being administered. Epidemiologist Miguel Hernan of Harvard University published a study on the effects of the vaccine in Israel over the past few weeks that confirmed that one dose can provide a high level of protection, but also pointed to the superior efficacy of the second dose. “Our results indicate that a single dose is effective, although not as effective as two doses,” he says. “This is not surprising. It was already seen in the clinical trial. It will be interesting to see in future studies whether spacing the doses further apart increases effectiveness after the second dose.”

As we have seen time and again during this pandemic, choosing strategies is a matter of risk management as decisions have to be made based on incomplete information. “As of today, there is no solid data to confirm the superiority of using existing vaccines to prioritize first doses [as the UK does] rather than to complete the vaccination regimen in three-to-four-4 [as virtually all other countries do],” says Hernan. “With the information currently available, both strategies can be justified. Fortunately, in two to three months, when vaccine availability is much greater, this debate will cease to be relevant.”

English version by Heather Galloway.

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