Corona virus disease

Coronavirus disease (COVID-19) is an infectious disease caused by the SARS-CoV-2 virus.
Most people who fall sick with COVID-19 will experience mild to moderate symptoms and recover without special treatment. However, some will become seriously ill and require medical attention.
How It spread
The virus can spread from an infected person’s mouth or nose in small liquid particles when they cough, sneeze, speak, sing or breathe. These particles range from larger respiratory droplets to smaller aerosols.
You can be infected by breathing in the virus if you are near someone who has COVID-19, or by touching a contaminated surface and then your eyes, nose or mouth. The virus spreads more easily indoors and in crowded settings.

Main causes of COVID-19

COVID-19 is caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus strain.

What are the primary symptoms of COVID-19?

Some of the primary symptoms to look for in a Covid 19 infected person are fever, dizziness, breathlessness, headache, dry cough ( eventually result in phlegm) and in a few cases loss in smell and taste. A few cases have also reported diarrhoea and fatigue.

Precautions for covid

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COVID-19 vaccine
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Stopping the spreadstarts with you
Wear a mask.
Clean your hands.
Maintain safe distance.
Get vaccinated.
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General public health information
Protect yourself and others around you by knowing the facts and taking appropriate precautions. Follow advice provided by your local health authority.
Check with your local health authority for the most relevant guidance for your region.
To prevent the spread of COVID-19:
Maintain a safe distance from others (at least 1 metre), even if they don’t appear to be sick.
Wear a mask in public, especially indoors or when physical distancing is not possible.
Choose open, well-ventilated spaces over closed ones. Open a window if indoors.
Clean your hands often. Use soap and water, or an alcohol-based hand rub.
Get vaccinated when it’s your turn. Follow local guidance about vaccination.
Cover your nose and mouth with your bent elbow or a tissue when you cough or sneeze.
Stay home if you feel unwell.
If you have a fever, cough and difficulty breathing, seek medical attention. Call in advance so your healthcare provider can direct you to the right health facility. This protects you, and prevents the spread of viruses and other infections.
Masks
Properly fitted masks can help prevent the spread of the virus from the person wearing the mask to others. Masks alone do not protect against COVID-19, and should be combined with physical distancing and hand hygiene. Follow the advice provided by your local health authority.

Covid 19 vaccination
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Equitable access to safe and effective vaccines is critical to ending the COVID-19 pandemic, so it is hugely encouraging to see so many vaccines proving and going into development. WHO is working tirelessly with partners to develop, manufacture and deploy safe and effective vaccines.

Safe and effective vaccines are a game-changing tool: but for the foreseeable future we must continue wearing masks, cleaning our hands, ensuring good ventilation indoors, physically distancing and avoiding crowds.

Being vaccinated does not mean that we can throw caution to the wind and put ourselves and others at risk, particularly because research is still ongoing into how much vaccines protect not only against disease but also against infection and transmission.

See WHO’s landscape of COVID-19 vaccine candidates for the latest information on vaccines in clinical and pre-clinical development, generally updated twice a week. WHO’s COVID-19 dashboard, updated daily, also features the number of vaccine doses administered globally.

But it’s not vaccines that will stop the pandemic, it’s vaccination. We must ensure fair and equitable access to vaccines, and ensure every country receives them and can roll them out to protect their people, starting with the most vulnerable.

How effective is a single vaccine dose against Covid-19

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The cases are already beginning to emerge.

When 85-year-old Colin Horseman was admitted to Doncaster Royal Infirmary in late December, it was for a suspected kidney infection. But not long afterwards he caught Covid-19 – at the time, roughly one in four people in hospital with the virus had acquired it there. He developed severe symptoms and was eventually put on a ventilator. A few days later, he died.

At first glance, Horseman’s situation may seem fairly typical, though no less tragic for it. After all, at least 84,767 people have now succumbed to the disease in the UK alone at the time of writing. But, as his son recently explained in a local newspaper, less than three weeks earlier he had been among the first people in the world to receive the initial dose of a Covid-19 vaccine – the Pfizer-BioNTech version. He was due to receive the second dose two days prior to his death.

In fact, most vaccines require booster doses to work.

Take the MMR – measles, mumps and rubella – vaccine, which is given to babies around the world to prevent these deadly childhood infections. Around 40% of people who have received just one dose are not protected from all three viruses, compared to 4% of those who have had their second. People in the former group are four times more likely to catch measles than those in the latter – and there have been outbreaks in places where a high proportion of people have not completed the full MMR vaccination schedule.

“The reason that people are so keen on boosters and consider them so vital is that they kind of send you into this whole other kind of fine-tuning mode of your immune response,” says Danny Altmann, professor of immunology at Imperial College London.

How booster vaccines work

When the immune system first encounters a vaccine, it activates two important types of white blood cell. First up are the plasma B cells, which primarily focus on making antibodies. Unfortunately, this cell type is short-lived, so although your body might be swimming in antibodies within just a few weeks, without the second shot this is often followed by a rapid decline.

Then there are the T cells, each of which is specifically tailored to identify a particular pathogen and kill it. Some of these, memory T cells, are able to linger in the body for decades until they stumble upon their target – meaning immunity from vaccines or infections can sometimes last a lifetime. But crucially, you usually won’t have many of this cell type until the second meeting.

The booster dose is a way of re-exposing the body to the antigens – the molecules on pathogens that trigger the immune system – to initiate part two of the response. “You’ve kicked in all this fancy stuff,” says Altmann. “So, once you’ve had your boost you’ll have a higher frequency of memory T cells and ditto to some extent for the size of the pool of memory B cells you’ll have. They’ll also be making higher quality antibodies.”

On second exposure to the same vaccine or pathogen, the B cells that remain from before are able to rapidly divide and create a menacing throng of descendants, leading to a second spike in the amount of antibodies circulating.

How long does it take to have immunity after the second vaccine dose?

Both the Pfizer-BioNTech and Moderna vaccines work by introducing your immune system to a part of the new coronavirus called the spike protein. This protein is found on the viral surface. It’s used to help the virus bind to and enter host cells in your body.

Because your immune system has a memory, it can use the vaccine to analyze and store information about the spike protein. It can then draw upon this information to protect you if you’re exposed to the actual virus in the future.

However, immunity doesn’t happen immediately after vaccination. In fact, it typically takes about 2 weeks for your body to build up immunity. Because of this, you can still become ill during this time frame.

Now that we’ve discussed how long it generally takes to have immunity, let’s take a look at the effectiveness of the Pfizer-BioNTech and Moderna vaccines in the weeks after the second dose.