CORONAVIRUS

Spain among world leaders in administering second Covid-19 dose, but strategy under debate

Only five countries have vaccinated a higher percentage of the population with the two shots, but a growing amount of data suggests that it is better to immunize more people with one jab as soon as possible

A health worker administers a Covid vaccine in a bar in Tel Aviv.
A health worker administers a Covid vaccine in a bar in Tel Aviv.GIL COHEN-MAGEN / AFP

Spain is one of the countries that has administered the highest percentage of the population with the second dose of the Covid-19 vaccine: 2.4% have received the two jabs, meaning they have the full protection offered by the vaccine. According to figures from Our World in Data, which is run by Oxford University in the United Kingdom, Spain is only behind Israel – which is the clear world leader, with nearly a third of the population fully vaccinated – the United States (4.83%), Denmark (2.99%), Romania (2.74%) and Serbia (2.67%).

But while this is good news – it means that the vaccines are being administered at a good speed as they are delivered – there is another side to the coin. Studies indicate that just one dose of the vaccine can provide a high level of protection from Covid-19. This means that every second dose administered could be seen as a jab that didn’t go toward protecting another person.

The vaccination drive in the United Kingdom is following this principle. While Spain has administered a higher percentage of the population with the second dose than the UK, it is far behind the country with respect to the first jab. In Spain, 3.5% of the population has received the first Covid dose, compared to 25% in the UK. This approach from the government of Prime Minister Boris Johnson was initially viewed with skepticism, but a growing amount of research has come to support it.

A study published last Friday in the medical journal The Lancet shows that the Pfizer-BioNTech vaccine is 85% effective in symptomatic infections after the first dose. The investigation, which involved more than 7,000 workers at the Sheba Medical Center in Tel Aviv in Israel, found a dramatic reduction in infection rates between 15 and 28 days after the first inoculation, reports Juan Carlos Sanz. With respect to total coronavirus infections, including asymptomatic cases, the Pfizer vaccine was found to be 75% effective. The findings come after two Canadian scientists published a letter in the New England Journal of Medicine arguing that the first dose of the Pfizer vaccine was 92.6% effective, according to studies from the pharmaceutical company itself and the US administration.

Although the Canadian scientists admit that there are doubts about how long the protection from one dose lasts, they argue that administering a second jab after just a month has fewer short-term benefits. They write: “Given the current vaccine shortage, postponement of the second dose is a matter of national security that, if ignored, will certainly result in thousands of Covid-19-related hospitalizations and deaths this winter in the United States – hospitalizations and deaths that would have been prevented with the first dose of vaccine.”

Spain is following the guidelines of regulatory bodies: administer the second dose when it is the time, according to the vaccine’s instructions. Amós García Rojas, the president of the Spanish Vaccinology Society, says that new studies must be examined as they are published in order to decide whether this vaccination strategy must change, admitting that a lot can change very quickly depending on the new data. But for now, he supports following the protocol established by the European Medicines Agency (EMA), especially given that doses are expected to arrive more quickly, meaning the population can be vaccinated at a faster speed.

In the case of the vaccine developed by Pfizer, the EMA recommends waiting 21 days before administering the second dose, but admits that this period can be extended to 42 days without having an impact on the vaccine’s effectiveness. These 21 days are not trivial. At Spain’s current speed, 1.3 million people could be vaccinated with the first dose in this period. With respect to the Covid vaccine from Moderna and AstraZeneca, the recommendation is to wait 28 days and 12 weeks, respectively, before administering the second dose.

Spain has already updated its vaccination protocol once before. In response to studies that showed that people who had contracted the coronavirus developed a strong immune response, the Health Ministry recommended that an individual should wait six months from the date of their diagnosis before getting vaccinated.

Impact of vaccination drive starting to show

All signs indicate that Spain is starting to see the effects of the vaccination drive, which was launched at the end of December. Care homes, where more than 90% of residents have received the two doses, are showing increasingly more hopeful figures. Outbreaks in social service residences have fallen by 75% in the last month, more than double the drop recorded outside of these centers. And a growing number of Spain’s regions is reporting falls in new coronavirus cases and Covid-19-related deaths.

One of the clearest cases of this fall is Asturias, which was also the Spanish region that most quickly vaccinated care home residents. The graph below shows the weekly number of coronavirus victims inside and outside of social service residences. While at the beginning of 2020, the two categories followed the same pattern, they started to diverge three weeks into the vaccination drive. The delay is understandable given that the vaccine can take between 10 and 12 days to have an effect and that the number of fatalities is the last data point to reflect a fall in contagion. But three weeks after the launch of the vaccination campaign, the lines on the graph began to diverge, and the number of deaths outside care homes continued to rise, while deaths inside care homes plummeted.

For this to be considered solid proof of the vaccine’s impact a study analyzing the data and removing other possible factors is needed. But Mario Margolles, the director of the Asturian Health Observation, has few doubts about what the figures mean. “It is evident that [the vaccines] are having an effect, because all the other factors are the same and we are seeing a fall in mortality from the first dose. Seeing this makes us very excited and gives us a feeling of great relief,” he says. The third wave of the coronavirus hit Asturias a little later than the rest of Spain, and according to Margolles, this meant that the vaccine had more time to have an impact and prevented hundreds of deaths. Margolles also admits that the immunization drive has shown that the vaccines are not 100% effective. As studies indicate, they do not work in at least 5% of cases. “We are seeing some cases who get infected more than a week after the second dose, but that was to be expected,” he explains. Studies, however, have shown that those who contract the coronavirus after receiving the vaccine have a much lower viral load, meaning the virus causes less serious symptoms or no symptoms at all, and transmission levels are lower.

English version by Melissa Kitson.

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