Flu and Corona - is the double wave coming?

Corona numbers are rising again – and besides, flu season is upon us. Above all, a double wave could push hospitals to their limits, experts warn. But there are solutions.

Why is a new flu wave threatening today?

The flu season has hardly taken place in the past two winters, in particular due to the obligation to wear a mask, distance rules and contact restrictions. In many areas, these measures have now been relaxed or disappeared altogether. It must be assumed that there will probably be a new wave of flu this winter, said Carsten Watzl, secretary general of the German Society for Immunology, on SWR radio.

Viruses generally spread more easily during cold times of the year. Aerosols can remain suspended in the air longer when the air is rather dry – and it is precisely winter heating that dries the air indoors. Our mucous membranes are also generally drier and become more vulnerable to viruses, especially in cold weather.

Will the flu epidemic be stronger than before the pandemic?

It is difficult to estimate the extent of the flu epidemic. Even before the start of the pandemic, the number of cases fluctuated from year to year. In Australia, the flu season is currently coming to an end. The balance sheet shows that there was a flu wave, that it started earlier and that it was stronger than before the pandemic. But the wave of flu was quiet there, according to Watzl. It assumes that an average flu season can also be expected here as before the pandemic.

Who is particularly exposed to contagion?

Unlike before the pandemic, many people have not been in contact with the flu virus for a long time. Young children in particular have not been infected for the first time: They do not yet have immune protection and are therefore more vulnerable to infection. Australian figures show it: More than 50 percent of flu cases are in children under the age of 16. But in them, the disease is usually less severe.

Who should get the flu shot?

Serious developments are especially to be expected in the elderly and people with weakened immune systems. In this case, the flu can also have a fatal outcome. According to the Robert Koch Institute (RKI), around 25,100 people died in Germany from influenza infection during the 2017/2018 flu season.

In Germany, the Standing Committee for Vaccinations (STIKO) therefore calls on, among others, people aged 60 and over, pregnant women and people with chronic illnesses to get vaccinated against influenza. Vaccination is also recommended for people in frequent contact with other people. These include workers in the healthcare sector and residents of retirement and care homes.

To be protected in time, the RKI recommends getting vaccinated between October and mid-December. Vaccine protection is complete after 10 to 14 days. Vaccination is done both at the family doctor and in pharmacies.

What protection does the flu vaccine provide?

Each year, a different variant of the flu virus dominates. And each year, it is necessary to predict in advance which variant could pose a problem the following season in order to have a vaccine ready in time.

These predictions do not hold true every year in the same way. It is possible that the dominant influenza viruses do not correspond exactly to the viral strains contained in the vaccine, because other viral strains have established themselves in the meantime. This is why the protection offered by the flu vaccine also varies.

According to the RKI, studies show that the effectiveness of the flu vaccine has consistently been between 20 and 60 percent over the past decade. But even in a year when the efficiency is relatively low, many cases of illness can be prevented. The data also show that the disease is less severe in vaccinated people.

According to the RKI, simultaneous vaccination against influenza and coronavirus does not have a negative influence on the protective effect of the vaccine. However, reactions to the vaccine may be a little stronger in this case.

How does an immune response work?

Vaccination prompts the body to produce antibodies. These appear within days or weeks thanks to specialized blood cells. Immunologist Carsten Watzl describes antibodies as an “army” which must grow as quickly as possible through cell division. If the real pathogen enters the body again, it is armed. Antibodies block the binding site of the virus, and the virus can no longer infect cells in the body.

Cells that are already infected are simply destroyed by T lymphocytes, commonly called killer T cells. The spread of the disease in the body is thus prevented.

The second important part of the immune reaction is made up of so-called memory cells. These exist both in B cells, responsible for the formation of antibodies, and in T cells. After an infection, the body produces these memory cells which carry with them information about a pathogen such as SARS- CoV-2. In the event of a new infection, they can initiate the immune response within a day, produce antibodies and form specific T cells. The virus can thus be combated quickly. The same seems to be true for SARS-CoV-2, the researchers assume. They were able to show that genes form memory T cells that remain in the body for a long time.

Is simultaneous contamination by the coronavirus and the flu possible?

A double infection with Corona and flu viruses is rather rare. This is because the immune system activates non-specific defense mechanisms during a viral infection. This is because if a cell is already infected with a virus, it sends out messengers which, in turn, put other cells into a sort of lockdown mode. Thus, not only is the current viral infection contained, but it also becomes more difficult to become infected with other viruses.

What would be the consequences of a simultaneous wave of coronavirus and flu?

A double wave of Corona and flu could pose a problem at the societal level, warns Professor Watzl. Hospitals could then reach their load limit again, he fears.

The numbers for serious respiratory illnesses are currently on the rise. However, according to the RKI’s weekly report, this figure also includes cases “hospitalized or requiring intensive care due to another illness and for whom the diagnosis of Sras-CoV-2 is not at the forefront of the disease. or treatment”.

Infected patients not only need more care, but they also need to be isolated so as not to infect others in the hospital. In addition, a high number of infections could lead to increased absences of care and health personnel, which could possibly worsen the situation in hospitals.

Immunologist Watzl, however, is optimistic about the absence of a violent double wave, given the currently dominant omicron variant, for which the infection is generally less severe, and the high background immunity in the population thanks to the vaccinations and overcome infections.