At the start of the year, few people had heard of Wuhan, the R number and herd immunity.

A close contact was a sound source for a journalist.

Social distancing was a deliberate avoidance of people not much liked.

And flattening the curve was a post-festive season diet programme.

But everything has changed.

This year, old words took on new meaning and new words entered the popular lexicon.

Covid-19 is not a discerning virus and has touched the famous and those less so.

French President Emmanuel Macron, US President Donald Trump, British Prime Minister Boris Johnson have been among the good and the great to catch the virus.

If the start of the year was marked by fear, the end of the year has brought some hope.

The arrival of vaccines is a significant milestone.

But there needs to be realism over how quickly people will be immunised in Ireland and how long it will take to have a noticeable impact on how we currently work and live.

As of now, vaccination will not end social distancing, mask wearing and public health measures.

This is because there are big unknowns about vaccination, in particular - will people who are vaccinated still transmit the virus to others?

Some vaccines may be better in this regard than others but it will take time to establish that.

It means that talk of vaccination certificates may be of limited value if the vaccine does not halt spread.

Emmanuel Macron (left) and Boris Johnson both contracted Covid-19

The other imponderable is how long vaccination will provide protection for and will it require an annual vaccination for people, as with the flu jab.

The vaccination plans now in place may be quite different in a few month's time, when more data emerges.

On Monday, an expert panel of the European Medicines Agency will meet to evaluate the Pfizer-BioNTech vaccine, which has yet to be approved for use in the EU.

Vaccination of the population against Covid-19 is a complex project, never undertaken before.

Even preparing the Pfizer-BioNTech vaccine for administration is complicated.

Vials of thawed vaccine must be removed from the refrigerator. It is a concentrate vial, so it has to be diluted. Syringes then have to be prepared for administration.

One vial usually contains enough vaccine for five syringes/administrations when diluted. Some early reports from the US have suggested that vials may actually contain enough vaccine for six to seven doses when diluted.

Once removed from a refrigerator and stored at room temperature, vials must be diluted within two hours and then used within six hours. There is much that could go wrong when preparing the vials.

Vaccines may become viewed as something rare and valuable during the early part of next year. That could result in vaccine tourism developing, whereby some people will be able to travel to countries where vaccination is being offered faster.

A small amount of vaccine, enough for around 5,000 people to be immunised, is expected in the first batches here.

The best guess is that it will likely be the middle of next year, or a bit later, before most people are offered the vaccine.

So it means that 2021 will look a lot like 2020 for a while - but it should be quite different too.

Vaccines may become viewed as something rare and valuable during the early part of next year.

That could result in vaccine tourism developing, whereby some people will be able to travel to countries where vaccination is being offered faster.

While governments will want to ensure vaccines are provided only by the public health system, where there is a market, the private sector often steps in. Poorer countries will also need help to access vaccines if the world is to tackle this threat properly.

Vaccination here will be free and not mandatory.

In Ireland, people will not have to take a vaccine, if they do not wish to.

A report this week by the Health Information and Quality Authority looked at the factors influencing vaccination and Covid-19.

It noted that there is precedence with certain travel vaccines – a requirement for evidence of yellow fever vaccination in order to be permitted to enter some countries.

There is much that could go wrong when preparing the vaccine vials

Some countries also require evidence of childhood immunisation for school entry.

But HIQA concluded "there may be significant ethical and organisational issues surrounding any mandatory vaccination policy for a workforce in the context of Covid-19".

HIQA said the success Ireland has achieved in relation to Covid-19 has largely been based on consensus, rather than penalties and enforcement and that this should be considered in informing vaccination policy.

2020 has been a year of remarkable events, unparalleled in world history. 

So there is an added surrealism that on 21 December, and not since 1623, Jupiter and Saturn will align to become what many believe was the famed Star of Bethlehem.

These are the two largest planets in our solar system and they will be closest on 21 December in what is termed 'The Great Conjunction’ by astronomers.

It will all be visible with the naked eye, weather permitting.

On this island, there is a contrasting landscape of how services are coping with the virus.

Only this week there were stark pictures of the overloaded health system in Northern Ireland, with ambulances caring for patients in the car park of Antrim Hospital.

In a posting on social media, public health physician, Dr Gabriel Scally warned that the island of Ireland was in trouble. He said that the population was not safe unless Covid-19 was controlled across all of the island.

"Northern Ireland doesn’t have a functioning public health response to Covid, and its people are paying a high price," he said.

Patients had to be treated in the car park of Antrim Hospital

In the NHS in Britain, the number of hospital patients with Covid-19 is on the rise again and there are fears about a third wave.

Germany, Italy and the Netherlands have also put tougher measures in place.

There are genuine fears here that the relaxation of restrictions for Christmas - that began yesterday - may further boost case numbers - with 582 new infections reported last night.

How difficult will it be for the HSE to track and trace the final contacts of this group? And publish hard details which does not breach private information?

Especially, given they have had to deal with much bigger daily case numbers of over 1,200.

The public needs maximum information for full buy-in.

Meanwhile, the festive period is always a challenge for the health system.

Influenza cases, outbreaks of norovirus, increased admissions of frail older people and inclement weather add to those pressures on beds.

If a third Covid-19 surge is put into that mix, it could pose a serious threat.

For that reason Government and public health experts are urging people to stick with the consistent messages about socialising, with Christmas Day just another six days away.

On Thursday, the Taoiseach flagged that a return of restrictions was being planned here earlier than expected – sometime before New Year’s Eve.

On Tuesday, Cabinet will issue its early prescription for the expected post-Christmas hangover.

The return to restrictions is not unexpected but it is coming earlier than people might have anticipated.

Announcing the measures this early, could itself fuel more social activity than might otherwise have occurred in the lead-up to Christmas, as the closing bell looms on hospitality and new limits on household visits are planned.

The closing bell looms for the hospitality industry again

Closing hospitality - especially around New Year’s Eve - may result in more house parties in uncontrolled environments. In contrast, the hospitality sector insists that its pubs and restaurants are controlled environments, with low figures as regards outbreaks, so far.

There has been a huge volume of data on Covid-19 and its impact on Ireland. But there has been a lack of precise data in some areas too.

People want to see the hard Irish data, rather than international data, behind cases in restaurants, cafés, pubs, weddings and funerals here.

The argument being if the figures exist, why not use them? Otherwise, it can fuel a perception that the hard information is not there, due to the limitations of the HSE test and trace system and not being able to go back and find the original source of the virus.

That is a recipe for ongoing discontent and division over some restrictions.

Ireland, like many countries, uses the PCR test system for detecting the virus. While it is viewed as a Gold Standard, it has its limitations too.

This month, the World Health Organization issued an instructions-for-use notice for countries using PCR testing for the virus, in particular on the elevated risk for false results, in some circumstances.

The WHO said that the probability that a person who has a positive result is truly infected with the virus decreases, as the positivity rate decreases, irrespective of how specific the test is.

So health services are advised to take into consideration testing results along with clinical signs, symptoms and confirmed status of any contacts.

The WHO said the design principle of PCR means that for patients with high levels of circulating virus (viral load), relatively few test cycles will be needed to detect the virus and so the cycle threshold (Ct) will be low.

"Conversely, when specimens return a high Ct value, it means that many cycles were required to detect virus. In some circumstances, the distinction between background noise and actual presence of the target virus is difficult to ascertain," the WHO noted.

Ireland, like many countries, uses the PCR test system for detecting the virus

So those involved in PCR testing have to be constantly aware and adjust for the risk of false positive and negative Covid-19 results.

On Thursday, the HSE issued a strong warning in very stark terms for the period ahead - to only meet people indoors "that you trust with your life".

While the virus is a frightening prospect, the statement was also a frightening one.

It also appeared to go further than the spirit of the current legal restrictions, whereby people have been allowed have more careful social and family gatherings and also since yesterday have been able to leave their county. 

While the HSE warning was clearly intended as a public health message, it may also have a chilling effect on some Christmas gatherings, if people feel invitees are to be essentially vetted before coming to dinner.

At this stage of Ireland’s experience with Covid-19, people know what the necessary measures are. They are also adults who have gone through the toughest restrictions seen in modern times and know more restrictions are to come.

Was it necessary to use such stark language at this particular time, especially with many people already anxious, staying at home and doing all the right things - but also looking forward to meeting some family members for the first time this year?

This is my last long read Saturday piece for now, until we gather again in the New Year.

It has been an honour to try and chronicle the events around coronavirus, since I started these weekly online pieces in early March.

Social distancing will still be needed in 2021

For all those people who have been in touch with me during the year with their experiences, views and questions, I wish you all a Happy Christmas and a safe New Year.

Irish people undertook  a very difficult journey this year, with many twists and turns.

It was mostly done together, but at times apart, on some issues.

With Covid-19 we are hopefully on the journey home now and the expectation is that the pandemic will end sometime next year.

While there is much to look forward to in 2021, many things will stay the same for a while.

Social distancing, hygiene measures and some restrictions will still be needed.

A high performing HSE test and trace system will also be essential.

Some uncertainty remains, with unanswered questions about the virus and vaccines.

This has been a broken year, it has fractured people and shattered plans.

Over the year ahead, the task will be to try and repair the damage, physically and mentally.

While there is still some road to go, the journey home is about to begin.