Friday, January 28

The sixth wave accelerates after being the slowest of the pandemic so far

Infections have been increasing for more than 40 days, especially in the last week, which could indicate a change in behavior in the wave that is taking the longest to reach its peak of the entire pandemic. One in four Spanish cities have once again exceeded 500 cases of incidence and the positives have multiplied in the last two weeks until this Friday the incidence rate has exceeded the maximum risk of contagion threshold. But the curve drawn by parameters such as hospital occupancy, mortality and even cases is, for the moment, and we have yet to see how it evolves in the coming weeks, flatter than in other episodes. A phenomenon that experts attribute directly to vaccination, which has reached almost 38 million people at this point in the pandemic with the full schedule, in a context in which there are hardly any restrictions in force, compared to what happened in waves previous.

Spain enters the level of maximum contagion risk

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“The slowness of the wave that we are seeing is mainly due to vaccine coverage, which is already very widespread. This wave began with a very large percentage in almost all age groups with the approved vaccine and in a period where the cold and indoor activities, “says preventive medicine specialist Mario Fontán. When the weekly average number of cases detected daily in Spain began to rise, on November 1, 80.4% of the population already had at least one dose and 78.7% had the full schedule.

As can be seen in the graph above, the evolution of the cases that are detected daily in Spain during the sixth wave continues below the second, third and fifth, all of them much more explosive. Only in the fourth wave, which lasted just 28 days, the average number of daily cases remained below. “That occurred at a time when we were coming off a very powerful wave in January (2021) and there were fairly general measures to reduce transmission. The peak occurs in April, when the risk is already beginning to be reduced also by the situation and because of a set of containment measures that are not in place now, “explains Ildefonso Hernández, Professor of Public Health at the Miguel Hernández University and former Director General of Public Health of the Government of Spain.

Since the beginning of this sixth wave, more than 400,000 new infections have been registered in 45 days. The only wave that had been rising for almost as many days in a row was the third, last Christmas, which accumulated twice as many cases in two fewer days, until it began to decline, on January 21 of this year. The second wave added 440,000 cases to its peak, 29 days after it began in October 2020; and the fifth added 575,000 more cases to the total balance of infections during 36 days, between June and July. The fourth registered about 175,000 cases in 28 days.

What is important to highlight is that, although in the first waves there were fewer diagnoses due to the difficulties in performing PCR or antigen tests on the population, from the summer the same effect can be produced for the opposite cause. Since rapid tests are available in pharmacies, it is more difficult to track people who test positive if they do not report it. In addition, among the vaccinated population there could be more asymptomatic cases that are not detected.

The hospital admissions curve is also experiencing a slower rise for the time being. After 43 days, there are 4,730 more patients in the hospital than there were at the beginning of the wave. It is a less pronounced increase than in the second, third and fifth. Furthermore, this wave found Spain with a better hospital situation than the previous ones. Just before the second there were more than 10,000 people hospitalized. In 31 days the occupied beds had already doubled, with more than 20,000 patients admitted. The impact of COVID-19 on hospitals was much more noticeable in the third wave. Although it began with a situation more or less similar to the second, in this case it escalated in a month and a half to more than 30,000 hospitalized people.

To establish a comparison between this third wave and the current one, at this moment, 40 days after its start, the number of people who remain in a hospital bed has multiplied by four, reaching 6,300 hospitalizations. Between the beginning and the end of the fourth wave, hospital occupancy barely increased by some 3,000 admissions in just over a month. It ended in records similar to the fifth, with the difference that that wave began with about 7,500 people in hospitals and the next, with less than 2,500. In other words, the fifth wave increased hospital pressure faster than the fourth, but it came from a better situation.

“The effect that vaccination is having on reducing hospitalizations and in severe cases in general is obvious,” explains Hernández, who also points to other phenomena with less influence but which are also there, such as the vaccinated population that has passed the infection and risk groups who have also had the virus, who now have higher immunity, or in the most extreme cases, people who have died. In any case, the hospital saturation of the first waves of the COVID-19 pandemic is not being replicated at this time.

That milder rise that is appreciated, at least until today, is also being perceived in mortality. At the end of these lines, in the sixth wave it has reached 35 deaths, on average weekly. Very far from the peak of 110 that was reached in the fifth; 82 of the fourth; of the 543 of the third; or 337 of the second.

At the moment, almost a thousand people have died in the sixth wave. They are less than half of those that had accumulated during the same period in the previous wave and well below the 9,000 and 12,000 that perished during the shorter rises of the second and third, which happened before the massive administration of vaccines. In the case of the fourth, the number of deaths began to decrease much earlier, at 21 days, when almost 1,500 people had died.

“The major factor that can explain this mismatch between cases and income and deaths is vaccination. We already saw it a little in the fourth wave and more clearly in the fifth,” agrees Fontán. When the fourth wave began in mid-March, the immunization campaign had been underway since late December. By then, there were already almost 1.7 million people with the complete guideline, mainly the population at risk and the elderly. By the beginning of the fifth, on June 18, the number of people with a full guideline was already close to 14 million. When this began to take off, the experts already perceived that the initial profile of the new infections was different. Almost 60% were under 29 years of age, the group that at the beginning of the summer had not yet agreed or was beginning to access vaccination.

In this sixth wave, the groups that contribute the most infections to the total are those between the ages of 49 and 40 (one in five), 30 and 39 years (15%) and those under 9 years (12%). Precisely, the 5 to 12-year-old group has just joined the vaccination campaign this Wednesday, after receiving the Pfizer vaccine for children with the approval of the health authorities. In the case of adults between 30 and 49 years old, Fontán points to a context “in which there are no restrictions on these age groups in work or social settings and they have more interactions than other age groups”, something that could explain this situation.

What’s coming

Experts now doubt the evolution of this current wave, with Christmas around the weekend and omicron circulating. “We are in a situation in which the time until the cases with omicron are doubled is much shorter, so it is sensible to remember all the ventilation, distance and mask recommendations,” says Hernández. This professor of Public Health also recalls other factors to take into account, on which the increase or not of the number of cases will depend. On the one hand, “the risk behaviors of the population.” If mass gatherings indoors and without a mask are reduced, there will be fewer infections, he explains. On the other, “the speed at which the third dose of the vaccine is given.” “To the extent that it accelerates, it will protect itself a lot,” he says. This Thursday, Health has approved it for those over 40 and those vaccinated with AstraZeneca.

The normal thing is that the incidence rises and we have to prepare for it. If it doesn’t happen later, much better, but you have to put yourself in the situation and the health services have to be prepared

Ildefonso Hernandez
Former general director of Public Health of the Ministry of Health

All this occurs in a context in which, “as people are vaccinated, there is a certain prevention by the authorities when it comes to adopting very restrictive measures, so as not to interfere with life,” says Hernández, on the measures that are took last year around this time. Fontán agrees that with the administration of vaccines, “it costs more to implement any type of measure” and that although “it is one of the best tools we have, it will not do everything for us.”

In this sense, he advocates overcoming discourses that focus risk on family gatherings, but not on earlier dates. “It gives the feeling that infections arise exponentially at Christmas and that there are no previous levels of transmission that make things happen on those days. If we recommend that people be cautious at parties, but the day before we go to work or to the restaurant, the risk is there, “he explains.

In any case, experts advocate being alert, both at the care and response level. “The normal thing is that the incidence rises and we have to prepare for it. If it does not happen later, much better, but you have to put yourself in the situation and the health services have to be prepared,” says Hernández, who recalls that the wave of Flu usually has its highest incidence in the months of January and February. “That is one of the problems we have this year, because it makes services difficult by needing a differential diagnosis,” he explains.

“There cannot be an infinite transmission because the chains end up saturating themselves”, indicates Fontán. “As the contact patterns between people are not homogeneous, these chains become saturated because they cannot find anyone else to infect or because not everyone has the same possibility of being infected,” he continues. Now the process is slower, less explosive, and it may take longer to reach saturation. Day 45 of this sixth wave has not yet been reached.