Who to believe? Whose word should we trust? These are the urgent questions that many people are asking after almost a year of Covid-related chaos. While certain basic facts have been established about the virus, such as which groups are most vulnerable to it - overwhelmingly the frail and elderly - there remains much that scientists do not know, or cannot agree upon.
till, when it comes to a difference of medical opinion between the World Health Organisation (WHO) and the local anti-abortion group, Precious Life, I'll take the word of the global health authority. I think most reasonable people would do the same.
The WHO has strongly criticised a leaflet produced by Precious Life, warning people against having the Covid-19 vaccine.
The leaflet is alarmist in tone. It refers to "the dangers of 'rushed' vaccines", claiming that people who received them will "effectively be human guinea pigs". It raises concerns about the potential effect of vaccines on fertility, pregnancy and breastfeeding, and warns of "numerous reports" of people dying after getting the injection. Where are these "numerous reports"? No evidence is provided.
The WHO says that the Precious Life leaflet contains inaccurate claims which "put health and lives at risk".
In a carefully-worded statement, it tries to reassure expectant mothers who may be considering the vaccine: "Based on what we know about the mRNA vaccine, we don't have any specific reason to believe that there would be risks that outweigh the benefits of vaccination for pregnant women."
Here in NI, the Public Health Agency (PHA) says that existing non-clinical evidence has raised no concerns about safety in pregnancy. Nonetheless, the PHA says that since the vaccines have not yet been tested in pregnancy, those who are pregnant "should not routinely have this vaccine" until more information becomes available.
Likewise, Covid-19 vaccines are not thought to be a risk to breastfed babies, and the Joint Committee on Vaccination and Immunisation (JCVI) has recommended that they can be received by breastfeeding mothers.
As for any possible impact on conception, Dr Edward Morris, president of the Royal College of Obstetricians and Gynaecologists, said: "We want to reassure women that there is no evidence that Covid-19 vaccines affect fertility."
There is nothing wrong with women of childbearing age - or indeed anyone at all - researching the potential risks and benefits of the vaccine and deciding on the right course of action to take, according to their own personal circumstances. It's the sensible thing to do.
Those weighing up whether the vaccine is suitable for them should base their judgement on the best possible information available, from a range of well-informed, fully-evidenced sources. Not from an inflammatory, unscientific leaflet produced by hard-line activists.
Anti-abortion organisations have played fast and loose with the truth in the past. Stanton Healthcare, which describes itself as providing "up-to-date, medically accurate information" to pregnant women, opened a Belfast branch in 2015, in partnership with Precious Life.
In 2018, an undercover investigation found that the centre was falsely telling women that termination causes breast cancer and infertility. A counsellor at the Belfast clinic was secretly recorded telling an undercover reporter that having an abortion would make her breasts "fill with cancer".
In response, Professor Lesley Regan, the most senior gynaecologist in the UK, condemned the categorically untrue claims as "despicable", and a form of bullying. "To take advantage of a human being who is vulnerable and at risk is shameful," she said.
Everyone has got things wrong during the pandemic, even world-leading epidemiologists and virologists. Theoretical modellers, such as Professor Neil Ferguson, have produced wildly inaccurate projections.
Everyone is struggling to make sense of this new disease, how it behaves, and the best ways to protect the vulnerable from it.
The WHO itself has changed its advice many times, on issues such as the advisability or otherwise of wearing face masks. Science - especially the science of Covid - is a constantly evolving, politically contested arena, rife with vested interests.
The problem is not in getting facts wrong - which is, after all, precisely how science evolves, through a process of vigorous debate. It's in adapting the "facts" to suit a particular viewpoint.
In the case of Precious Life, it appears that the group's fundamental opposition to the vaccine rests on its claim that the inoculations "were developed using cell lines from aborted babies".
And who knows whether we can believe that or not?
When truth comes second to a one-dimensional ideological agenda, it's not truth any more. It's just a convenient means to an end.
